As the 2020 presidential debates begin, Biden maintains a solid lead

On November 3, 2020, a weeks-long presidential election between incumbent Republican Donald J. Trump and his Democratic challenger, former Vice President Joseph R. Biden, Jr., will end. In fact, as I write this, more than 1 million Americans have already cast their ballots.

With the first presidential debate scheduled to begin at 9 pm EST on Tuesday, September 29 at Case Western University in Cleveland, OH, here is an updated assessment of the 2020 presidential election; my previous assessment may be found here. These assessments are based upon all publicly-available polls of the presidential election—nationally and by state, recognizing presidential elections are determined by the Electoral College—conducted since January 1, 2019.

Table 1 lists the number of national polls assessing Biden vs. Trump conducted in each month of 2020 and in all of 2019, based upon the midpoint of polling field date; a handful of older polls were released since my last update. Sixty-eight pollsters, with an average B- FiveThirtyEight pollster rating, have assessed the 2020 presidential election at least once since January 1, 2019; 50 pollsters (mean B-/B) have assessed it more than once.

Table 1: Number of 2020 Monthly National Polls Assessing Biden vs. Trump

MonthBiden
2019107
January 202020
February 202025
March 202035
April 202050
May 202048
June 202062
July 202052
August 202079
September 202061
TOTAL539

Eighteen pollsters (mean B-/B) account for 73% of these polls, as well as 71% of the 432 polls conducted so far in 2020:

  • YouGov (B-), 69 polls (54 in 2020)
  • Morning Consult (B/C), 53 polls (47 in 2020)
  • Ipsos (B-), 39 polls (32 in 2020)
  • HarrisX (C), 31 polls (22 in 2020)
  • Emerson College (B+), 20 polls (8 in 2020)
  • Fox News; Beacon Research/Shaw & Company Research (A-), 19 polls (10 in 2020)
  • Change Research (C-), 18 polls (15 in 2020)
  • RMG Research (B/C), 17 polls (17 in 2020)
  • Data For Progress (B-), 16 polls (16 in 2020)
  • Rasmussen Reports/Pulse Opinion Research (C+), 16 polls (13 in 2020)
  • IBD/TIPP (A/B), 15 polls (10 in 2020)
  • Optimus/Firehouse Strategies (B/C), 14 polls (13 in 2020)
  • Redfield & Wilton Strategies (C+), 12 polls (12 in 2020)
  • Quinnipiac University (B+), 12 polls (8 in 2020)
  • Zogby Interactive/JV Analytics (C+), 11 polls (6 in 2020)
  • NBC News/Wall Street Journal (A-), 10 polls (8 in 2020)
  • ABC News/Washington Post (A+), 10 polls (7 in 2020)
  • CNN/SSRS (B/C), 10 polls (7 in 2020)

Figure 1 shows how Biden has fared monthly against Trump in 2020, using my weighted-adjusted polling averages (WAPA). I use pollster rating data to adjust for partisan lean (historic tendency to err more Democratic or Republican than other pollsters in analogous races) and quality.[1] I weight more recent polls higher, using the number of days since January 1, 2019 divided by 673, the number of days between January 1, 2019 and November 3, 2020. I then average two versions of WAPA: one treating polls by the same pollster as statistically independent, and one treating all polls by the same pollster as a single, time-weighted value; differences between estimates are usually negligible.

Figure 1

Using all polls conducted since January 1, 2019, Biden leads Trump nationally by 7.3 percentage points (“points”). This is very close to his September 2020 average of 7.2 points, down 1.7 points from his June peak. Biden’s margin rose from just over four percentage points in January and February, when he was fighting for the 2020 Democratic presidential nomination, to just under six points in the three months after Biden’s decisive win in the 2020 South Carolina Democratic presidential primary, to between seven and nine points since June 1, the day protesters were forcibly cleared from Lafayette Square so Trump could pose in front of St. John’s Episcopal Church holding a copy of the Bible.

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Again, though, presidential elections are fought across 50 states and the District of Columbia (“DC”), with the plurality winner in each state/DC winning every electoral vote (“EV”) from that state. Table 2 lists the number of polls within each state assessing Biden vs. Trump since January 1, 2019 and since January 1, 2020, plus that state’s 3W-RDM, my estimate of how much more or less Democratic than the nation a state has voted over the last three presidential elections; five states[2] and DC have not yet been polled.

Table 2: Number of state-level polls assessing Biden vs. Trump since January 1, 2019

State3W-RDMOverall2020
Wisconsin0.79885
Michigan2.29682
Pennsylvania-0.48778
North Carolina-6.08774
Florida-3.47365
Arizona-9.76860
Texas-15.35843
Georgia-9.64136
Minnesota1.52625
Ohio-5.82622
California23.22519
Iowa-4.72417
Maine5.91613
New Hampshire0.11611
Colorado2.21513
Kentucky-28.71412
Virginia1.51410
South Carolina-15.71311
Nevada2.0139
Montana-18.61211
Missouri-15.9119
Massachusetts22.187
Utah-33.187
Washington12.186
New York21.677
New Jersey12.077
Kansas-23.466
Connecticut12.864
Alabama-28.455
Mississippi-18.555
Oklahoma-38.155
Indiana-16.344
Alaska-19.243
North Dakota-29.442
New Mexico6.533
Tennessee-25.833
Maryland22.633
Delaware12.522
Arkansas-28.211
Hawaii34.311
Idaho-34.211
Louisiana-22.211
Oregon8.711
Vermont27.711
West Virginia-35.511
TOTALD-5.6928791

Twenty-one states have been polled at least 10 times since January 1, 2019, of which 19 have been polled at least 10 times in 2020. The five most-polled states are the closest states won by Trump in 2016—Michigan, Wisconsin, Pennsylvania and Florida—plus suddenly-swing North Carolina. Five other Republican-leaning states have been frequently polled: Arizona, Georgia, Texas, Ohio and Iowa, reflecting their status as ongoing or emerging battlegrounds. Light-blue Minnesota and dark-blue California (54 EV), round out the 12 states polled at least 20 times overall.

National averages still matter, though, as Table 3 illustrates. Combined with 3W-RDM, they provide the “expected Democratic-minus-Republican margin” in each state in 2020, all else being equal. For example, North Carolina has recently been 6.0 points less Democratic than the nation as a whole. Adding that to Biden’s current national margin (-6.0 +7.3 = +1.3) suggests Biden is slightly favored to win North Carolina in 2020, based solely on its recent voting history. And, in fact, Biden leads Trump by an adjusted mean of 1.4 points in 87 polls conducted in North Carolina since January 1, 2019.

Table 3: Expected and actual polling margins for Biden over Trump in each state in November 2020

State3W-RDMExpectedWAPAWAPA-Expected
DC82.089.4  
Hawaii34.341.729.1-12.6
Vermont27.735.021.8-13.2
California23.230.528.3-2.1
Maryland22.629.929.2-0.7
Massachusetts22.129.434.34.9
New York21.628.925.9-3.0
Rhode Island18.025.3  
Illinois14.722.0  
Connecticut12.820.117.9-2.2
Delaware12.519.819.2-0.6
Washington12.119.423.54.1
New Jersey12.019.318.0-1.3
Oregon8.716.012.1-3.9
New Mexico6.513.812.5-1.3
Maine5.913.213.30.1
Michigan2.29.67.0-2.6
Colorado2.29.511.11.6
Nevada2.09.34.2-5.1
Minnesota1.58.88.80.0
Virginia1.58.88.90.1
Wisconsin0.78.05.6-2.5
New Hampshire0.17.44.6-2.8
Pennsylvania-0.46.95.1-1.9
Florida-3.43.92.5-1.4
Iowa-4.72.6-1.2-3.8
Ohio-5.81.50.6-0.9
North Carolina-6.01.31.40.1
Georgia-9.6-2.2-0.61.6
Arizona-9.7-2.43.05.4
Texas-15.3-7.9-1.86.1
South Carolina-15.7-8.3-7.80.5
Missouri-15.9-8.6-6.22.4
Indiana-16.3-9.0-14.3-5.3
Mississippi-18.5-11.1-11.20.0
Montana-18.6-11.3-7.93.4
Alaska-19.2-11.8-4.37.5
Louisiana-22.2-14.9-8.36.6
Kansas-23.4-16.1-8.57.7
Nebraska-25.8-18.5  
South Dakota-25.8-18.5  
Tennessee-25.8-18.5-14.54.0
Arkansas-28.2-20.9-3.517.4
Alabama-28.4-21.1-15.45.6
Kentucky-28.7-21.4-18.62.8
North Dakota-29.4-22.1-20.41.7
Utah-33.1-25.8-13.812.0
Idaho-34.2-26.9-24.72.2
West Virginia-35.5-28.1-34.3-6.2
Oklahoma-38.1-30.8-22.97.9
Wyoming-45.7-38.3  
AverageD-6.4Biden+1.7*Biden+2.4+0.7

        * Only for the 45 states with both measures

The correlation between the expected margin and WAPA is +0.96, meaning polling matches expectations extremely well—as one increases or decreases, so does the other. Still, Biden is polling slightly ahead of those fundamentals, on average, meaning state-level polling as a whole is slightly better for Biden than his excellent national polling; that said, the difference mostly vanishes once you adjust for a state’s 2016 presidential election turnout.

Biden is underperforming expectations in some states, most notably Hawaii and Vermont, though each state has only been polled once. He is also underperforming in under-polled Nevada. Biden leads there by 4.2 points, about five points lower than the 9.3 points by which he “should” be leading. Biden is also underperforming expectations in Republican-leaning Indiana (-5.3) and Iowa (-3.8). By the same token, Biden is overperforming in the traditionally Republican states of Arkansas, Utah, Oklahoma, Kansas, Alaska, Louisiana and Texas; of these states, though, only Kansas and Texas have been polled more than five times. There is a partisan split in Biden’s over-and under-performance: in states with 3W-RDM>-5.0, Biden is underperforming by 2.5 points, on average. In states with 3W-RDM<-5.0, Biden is overperforming by 3.8 points. Many grains of salt are in order here, however. In recent elections, “fundamentals” have missed the final margin by an absolute value average of 5.4 points.

Still, the close alignment between the two values allows us to combine them into a single estimate of Biden’s margin over Trump on November 3, 2020, assuming polls become more predictive as an election gets closer:

  1. Assign expected value and WAPA equal weight as of January 1, 2020.
  2. WAPA weight increases daily with proximity to November 3, 2020.
  3. Weight all national and state polls conducted entirely after August 28, 2020—the final day of the Republican National Convention—twice as much as all earlier polls.

I also calculated how likely Biden is to win the EV from each state, assuming this likelihood is distributed normally:

  1. For expected margins, I use mean = -0.8 and standard error = 7.1[3]
  2. For WAPA, I use standard error = 3.0, the margin of error in most quality polls; this is an over-estimate, as pooling reduces the standard error of the resulting polling average.
  3. Combined probability Biden wins a state’s EV calculated the same way as predicted final margin

While these means and standard errors are somewhat arbitrary, albeit defensible, the final EV probabilities shown in Table 4 are in line with what other forecasters are saying, including FiveThirtyEight.com.

Table 4: Estimated final state margins and probability of winning EV, Biden vs. Trump, November 2020

StateEVP(EV): ExpectedP(EV): WAPAP(EV): OverallProjected Margin[4]
DC3100.0% 100.0%89.4
Hawaii4100.0%100.0%100.0%31.1
Vermont3100.0%100.0%100.0%23.0
California55100.0%100.0%100.0%28.5
Maryland10100.0%100.0%100.0%29.3
Massachusetts11100.0%100.0%100.0%33.8
New York29100.0%100.0%100.0%26.2
Rhode Island4100.0% 100.0%25.3
Illinois2099.9% 99.9%22.0
Connecticut799.7%100.0%99.9%19.0
Delaware399.6%100.0%100.0%19.5
Washington1299.6%100.0%100.0%21.5
New Jersey1499.5%100.0%100.0%18.7
Oregon798.4%100.0%99.8%14.1
New Mexico596.6%100.0%99.6%12.6
Maine496.0%100.0%99.7%13.3
Michigan1689.1%99.0%98.3%7.1
Colorado989.0%100.0%98.9%11.0
Nevada688.4%92.1%91.9%4.6
Minnesota1087.0%99.8%99.0%8.8
Virginia1387.0%99.9%98.8%8.9
Wisconsin1084.6%96.8%96.0%5.7
New Hampshire482.5%93.9%92.9%4.9
Pennsylvania2080.6%95.5%94.6%5.2
Florida2967.1%80.2%79.3%2.6
Iowa660.0%35.1%36.8%-0.9
Ohio1853.9%58.2%57.9%0.7
North Carolina1552.8%68.1%67.1%1.4
Georgia1633.5%41.9%41.4%-0.7
Arizona1132.6%84.3%80.6%2.6
Texas3810.9%27.2%26.2%-2.2
South Carolina99.9%0.5%1.1%-7.8
Missouri109.2%1.9%2.4%-6.4
Indiana118.5%0.0%0.8%-13.8
Mississippi64.6%0.0%0.5%-11.2
Montana34.4%0.4%0.8%-8.1
Alaska33.8%7.4%6.8%-5.6
Louisiana81.4%0.3%0.4%-9.2
Kansas60.9%0.2%0.3%-12.3
Nebraska50.3% 0.3%-18.5
South Dakota30.3% 0.3%-18.5
Tennessee110.3%0.0%0.1%-16.5
Arkansas60.1%12.2%9.3%-12.2
Alabama90.1%0.0%0.0%-18.3
Kentucky80.1%0.0%0.1%-21.1
North Dakota30.1%0.0%0.0%-21.1
Utah60.0%0.0%0.0%-14.8
Idaho40.0%0.0%0.0%-24.9
West Virginia50.0%0.0%0.0%-31.3
Oklahoma70.0%0.0%0.0%-26.8
Wyoming30.0% 0.0%-38.3

Five weeks before Election Day 2020, and with every caveat about voting during a pandemic, Joe Biden is strongly favored to be elected the 46th president of the United States. Multiplying Biden’s win probabilities of his likeliest path to 270 EV—the Clinton states (minus Nevada) plus Michigan, Wisconsin and Pennsylvania—yields a minimum likelihood of winning of 79.3%; this is only a rough probability given how correlated voting behavior is across demographically-similar states.

Moreover:

  • He is at least a 91.9% favorite in enough states—and by margins of at least 4.6 points—to earn him 278 or 279 EV, depending on what happens in Maine, which, along with Nebraska, allocates two EV to the statewide winner and one each to the winner of its Congressional districts. At this point, Biden would already have won the presidency.
  • He is favored roughly 4-1 to win the 11 EV of Arizona (+2.6) and the 29 EV of Florida +2.6), increasing Biden’s total to 318 or 319 EV.
  • He is favored roughly 2-1 to win North Carolina (+1.4), for an additional 15 EV, increasing Biden’s total to 333 or 334 EV.
  • The 34 combined EV of Ohio (+0.7) and Georgia (-0.7) are essentially toss-ups, meaning Biden has a roughly 75% chance to win at least one of them, increasing Biden’s total to between 349 and 352 EV, with a maximum of 368 EV (or 369 with one EV in Nebraska).

Plus, it might take only a sharp break by undecided voters and a modest polling error for Biden to win the 44 combined EV of Iowa (-0.9) and the ultimate prize—Texas (-2.2). Thus, while something in the low-to-mid 300’s currently appears the most likely EV total for Biden, 413 EV cannot be discounted.

Using the simplistic—perhaps even simple-minded—method of multiplying Biden’s probability of winning each state by its EV, then summing, yields a “projected” EV total of 348.5, essentially adding Michigan, Pennsylvania, Wisconsin, Florida, Arizona, North Carolina, and one of Ohio/Georgia to the states 2016 Democratic presidential nominee Hillary Clinton won.

Biden’s lead looks solid even after making either of two historically-valid assumptions:

Polls systematically overestimate Biden’s margins by 3.0 points.

In this scenario, Biden’s projected EV drops to 297.4, still 27.4 more than required. He would be favored at least 80% to win in enough states to win 239 EV, though he would also be favored by at least 70.7% in three additional states totaling 34 EV, getting him to 273 EV. Thus, even if Biden “only” wins the national popular vote by 4.3, he would likely still prevail, though the decisive states—New Hampshire, Pennsylvania and Wisconsin—would be decided by relatively narrow margins, with all votes possibly not counted for a week or more. I hasten to add that the product of the state-level win probabilities for this path is only 33.1%–suggesting Trump might be a very slight favorite in this scenario, in line with the Republican advantage in the Electoral College.

Polls systematically underestimate Biden’s margins by 3.0 points.

In this scenario, Biden’s projected EV are a landslide-level 391.8, 121.8 more than necessary; the product of the state-level win probabilities for the path of least resistance jumps to 94.0%. He would be favored at least 80% to win enough states to earn 352 EV, while being a roughly 3-1 favorite in Georgia and Iowa, for a total of 374 EV. Biden would even be a slight favorite (61.9%) in Texas, which he would be projected to win by 0.7 points. Based on only one poll, Biden would have a 33.2% chance of winning Arkansas’ 6 EV, plus a 14.4% chance of winning Missouri’s 10 EV and a 11.1% chance of winning Alaska’s 3 EV. The last presidential candidate to come close to 433 EV was Republican George H. W. Bush, who won 426 EV in 1988.

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You may have noticed a drift over the last month toward Trump in Florida, North Carolina and Georgia, and a slight drift toward Biden in Nevada, Wisconsin, Arizona and Iowa, even if the projected winner has not changed in any of these states. That is because of the large number of polls released in the month since the end of the two national party conventions—and especially since Labor Day, when voters traditionally begin to focus more closely on the upcoming elections.

Three things typically happen after Labor Day that can cause polls to tighten, if only slightly, as Figure 1 suggests has happened over the last three months:

  1. Pollsters shift from sampling all registered voters to sampling who they deem likely to vote. Historically, this has led to a 1-to-2 point shift toward Republicans.
  2. Voters “come home” to the party for whose candidates they typically vote after considering voting for a different candidate. This generally benefits the trailing candidate.
  3. Undecided voters begin to make their decisions, some not until just before they actually vote. Depending how many undecided voters there are, these can cause large polling shifts late in a campaign. That said, in national polls, only 9.1% are either undecided or are leaning toward a third-party candidate.

Table 5 compares WAPA before and after August 29, 2020 to see where the race has changed; for simplicity, both measures assumes all polls, even those released by the same pollsters, are statistically independent. Only the 20 states with at least two polls in both time frames are included. A positive “Delta” indicates movement toward Biden.

Table 5: Polling Margins, Biden vs Trump, Before and After August 29. 2020

StateThrough August 29, 2020After August 29, 2020Delta
Maine10.4015.405.00
Montana-8.86-6.802.06
Nevada3.765.141.39
Wisconsin5.066.231.16
Iowa-1.74-0.611.13
California28.5329.190.66
Arizona3.053.620.57
Minnesota8.048.330.29
Ohio-0.050.070.13
Missouri-6.58-6.530.05
Michigan6.876.66-0.21
Pennsylvania5.064.69-0.37
South Carolina-7.25-7.65-0.39
Virginia9.619.20-0.41
Texas-1.72-2.14-0.42
North Carolina1.810.86-0.95
Georgia-0.09-1.70-1.61
Florida3.891.46-2.44
Kentucky-16.97-20.54-3.56
Colorado11.938.28-3.65
AverageBiden+2.74Biden+2.66-0.08

There is scant evidence in these 20 states polls have tightened in the previous month. Biden’s position has improved by at least 1.0 points in the key states of Iowa, Wisconsin, Nevada and Maine (where a key EV is in play), as well as in red-leaning Montana. Biden’s position has likewise worsened in the key southeastern states of North Carolina, Georgia and Florida, as well as in dark red Kentucky and blue Colorado. Again, however, tight-as-a-drum Ohio aside, the polling leader has not changed in any state.

If I replace WAPA listed in Table 3 with one calculated using only post-convention polls—even in the 13 states with only one such poll—Biden’s projected EV drop by 7.9 to 340.6, primarily because his probability of winning Florida’s 29 EV drops from 79.3% to 68.5%. Nonetheless, Biden would be favored by at least 80% in states totaling 290 EV. And his “path of least resistance”—swapping out New Hampshire for Nevada—still has an 80.5% probability, suggesting this race remains remarkably stable.

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None of this is to say Biden is guaranteed to be elected president of the United States over the next five weeks. There are worrisome signs this year’s elections will not be conducted as efficiently and transparently as they could be. Delays in mail delivery—allegedly orchestrated by a newly-confirmed Postmaster General—could leave millions of votes uncounted because they did not arrive by November 3. Moreover, while Biden’s national polling lead has consistently ranged between four and 10 points over the last 21 months, a late-recovering economy or last-minute “October surprise” could erase this lead. For example, as I write this, it has only been one day since the New York Times announced it had obtained 15 years of Trump’s tax returns.

All that being said, however, unlike Clinton in 2016, Biden has a sufficiently-wide range of paths to 270 EV that I estimate he is at least an 80% favorite to be elected president of the United States on November 3, 2020—or whenever ballots are ultimately counted.

Until next time…please stay safe and healthy…


[1] I cut in half the number value assigned to a letter grade for any poll conducted since June 1, 2020 which samples adults instead of registered or likely voters.

[2] Rhode Island, Illinois, Nebraska, South Dakota, Wyoming

[3] The former value is the mean arithmetic difference between “expected” and actual D-R margins across 153 state-level contests in 2008, 2012 and 2016, while the latter value is the standard deviation of these values. I recognize this is not a standard error. However, using the value 13.6—the range of values covering 95% of all values divided by 1.96, the final EV projection changes by only 1.0.

[4] Assuming undecided voters split their votes evenly between Biden and Trump.

4 thoughts on “As the 2020 presidential debates begin, Biden maintains a solid lead

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