[Eds. note: As of September 5, 2022, you may find updated House Democratic majority probabilities on the home page. Probabilities are calculated two ways: 1) using all generic ballot polls since January 1, 2021, 2) and using polls conducted since Labor Day 2022.]
On March 31, 2021, nearly five months after Election Day 2020, Democrat Rita Hart finally conceded to Republican Mariannette Miller-Meeks in Iowa’s 2nd Congressional District (“CD”), dropping her challenge to her six-vote loss. This was a net win for the Republicans, as United States House of Representatives (“House”) Member Dave Loebsack, a Democrat, had not sought reelection to an 8th term.
Overall, Democrats lost a net of 13 House seats relative to Election Day 2018, going from a 235-200 majority to a 222-213 majority. This double-digit seat loss occurred despite Democrats winning a 3.1-percentage-point (“point”) majority in all votes cast for U.S. House – 50.8 to 47.7%; notably, this was a 5.5-point decline from 2018
Returning to 2020, though, political observers were shocked at the number of House seats Democrats lost, especially because they won the presidency and netted three United States seats, giving them a 50-50 tie broken by Democratic Vice President Kamala Harris. Anyone following this website since at least June 2017, however, should not have been at all surprised.
Figure 1, using data from the 26 House elections from 1970 (vs. 1968) to 2020 (vs. 2018), shows that change in national House vote percentage accounts for an astonishing (for social science) 83% of the variance in House seat gain/loss. Reassuringly, the ordinary least squares (“OLS”) regression fitted to the data crosses the y-axis very close to the origin: a 0-point change in vote percentage essentially equates to no change in seats, which makes intuitive sense.
Figure 1: Change in % Democratic of Total House Vote vs. Net Change in Democratic House Seats, 1970-2020
Removing the 2018-20 data point from the OLS regression, suggests a drop in the Democratic share of the total House vote of 5.5 points yields an estimated loss of…
Dem Seat Change = 3.21 * (-5.5) – 1.19 = -18.8
Based on election data from the previous 50 years, Democrats should have lost 19 seats I 2020, with a 95% confidence interval (“CI”) of 18-20 seats. Yes, Democratic leaders expected to pick up seats, but history presents a compelling counter-narrative: Democrats were extremely lucky to maintain their House majority, however slender.
But what about 2022, the first midterm election of the Administration of Democrat Joseph R. Biden, Jr., when Republicans only need to net five seats to regain the majority? Figure 2 shows how poorly the first House elections after a new president is elected go for that president’s party – and getting worse over time. Granted, there have only been nine such elections starting with the 1962 midterms of Democratic President John F. Kennedy. Still, excepting the first post-9/11 midterm election – when Republicans under President George W. Bush in 2022 gained eight House seats – the party controlling the White House has lost an average of 53 House seats in the last 30 years. The overall average since 1962 is a net loss of 24 House seats…which would give Republicans a 237-198 edge going into 2023; the median is only -15, which would give Republicans a 228-207 edge.
Figure 2: 1st Midterm Seat Loss by Newly-Elected White House Party, 1962-2018
Based on the OLS regression equation in Figure 2, meanwhile, Democrats would be expected to lose 47 seats in 2022, dropping them to a 175-260 minority. However, because there are only nine data points, there is a great deal of “wobble” in this estimate – the 95% CI is a nonsensical -4,002 to +3,909.
In other words, all we really know from these nine 1st-term midterm elections is that anything between a loss of 61 seats and a gain of eight seats is historically plausible, with something in the 15-25 loss range most plausible.
This brings us full circle back to my model…and the question of what the margin in the total House vote will be in 2022. A little algebra reveals that to maintain a slender 218-217 House majority going into 2023, Democrats need to win the total House vote by at least 2.1 points – and likely at least 3.1 points (no net change) to account for a +/-1 seat 95% CI.
For comparison, political scientist Alan Abramowitz just published a model of net Democratic House seat gain. The two independent variables are 1) national House vote total (as opposed to change from previous election) and 2) number of House seats currently occupied by the president’s party. Those two variables account for 83% of the variance, as much as my single independent variable does. That said, Abramowitz’s model uses data from 1946-2018, giving him an additional 11 data points: 37 vs. 26. According to this model, Democrats would need to win the national House vote by about 6 points to maintain control, which equates to an increase of about 2.9 points from 2020.
Neither model is wrong, per sé. We are both trying to model a relatively infrequent occurrence while zeroing in a very precise outcome – the difference of a few seats – leading to the magnification of what really are small differences in outcomes. A 3-point lead and a 6-point lead are relatively close, and we agree Democrats have an uphill battle to retain the House, even without taking into account changes in CD lines due to reapportionment following the 2020 Census.
Technically, Abramowitz models Democratic lead on the “generic ballot question,” a variation of the poll question “If the election in your CD were held today, would you vote for the Democrat, the Republican, or some other party – or not vote at all.”
I recently compiled the results of the 20 generic ballot polls released publicly in 2021 then used the following steps to calculate a weighted-adjusted polling average (“WAPA”):
- Adjust raw margin – Democratic % minus Republican % – for “pollster bias,” as calculated for 538.com Pollster Ratings. Essentially, this is how much the pollster missed the final margin, on average, in recent polls of the same race.
- Average adjusted margins by how far the poll was conducted from Election Day 2022 – using midpoint of poll field dates – and 538.com pollster quality.
- Time weight: (677 – days to Election Day)/677
- Pollster weight: Numeric value of letter grade (A+ = 4.3, A = 4.0, etc.) divided by 4.3.
For example, the most recent generic ballot poll was conducted by Quinnipiac University from May 18 to May 24, 2021; it shows Democrats leading 50-41%. Quinnipiac has a historic Democratic skew of 0.5 points, meaning that 9.0-point lead is effectively an 8.5-point lead. The field midpoint was May 21, 2021, or 536 days until November 8, 2022, giving the poll a time weight of (677-536)/677 = 0.208. Their A- rating equates to a 3.7/4.3 = 0.860 pollster weight. Overall, this adjusted Democratic lead of 8.5 points has a weight of 0.208 * 0.860 = 0.179 – which, while not especially high, is highest among the 20 polls.
The raw average of these 20 polls is Dem+4.1, though mean Democratic bias of 0.5 points means this average is effectively Dem+3.6. Two polls without a 538.com pollster rating/bias were clearly conducted on behalf of Republicans, one in early April by PEM Management Corporation and one in late February by the National Republican Senatorial Committee. I traditionally used 1.5 as the bias for such polls, but I chose to match the most Democratic leaning poll in the 20: 3.5 for RMG Research. I also somewhat arbitrarily assigned these polls a letter grade of C; overall average was B-.
The initial WAPA I calculated was Dem+3.9, though it treated the multiple polls from RMG Research (2), McLaughlin & Associates (3) and Echelon Insights (4) as statistically-independent, even though polls conducted by the same firm are likely related. I thus calculated a second WAPA, which was the pollster-quality-weighted average of the bias-adjusted, time-weighted WAPA for each pollster. Basically, it is WAPA adjusted for pollster. This value was Dem+3.1
Averaging these WAPAs yields my best estimate of the November 2022 generic ballot as of June 2021: Dem+3.5. This is astonishing because it means support for Democratic House candidates increased 0.4 points since November – when, historically, support for the “out party” should be increasing.
If, in fact, Democrats win the national House vote by 3.5 points in November 2022, I estimate they would gain 0.3 seats, albeit with a 95% CI of -4.1 to +4.8 – which means they would have approximately a 94% chance of retaining the House. The Abramowitz model, however, estimates a 9-seat loss in this scenario – losing the House in the process.
It is not at all clear, of course, how well a 3.5-point lead in June 2021 translates to actual voting in November 2022. My poli-sci-sense suggests this lead – fairly robust since January, mind you – will slowly fade over the next year-plus due to a traditional complacency on the part of infrequent voters, in this case Democrats who may reason that as long as Biden is president, they do not need to vote in 2022, and a renewed enthusiasm on the part of out-party voters. This differential in voting enthusiasm, I suspect, is what leads to lopsided out-party victories in midterm elections.
Another reason for extreme caution is that this Dem+3.5 margin equates to Democrats 44.6%, Republicans 41.1%, Other/Undecided 14.3%. If Other earns the same 1.5% it did in 2020, that leaves fully 12.8% of voters up for grabs. It is not unreasonable – given voting enthusiasm differences – they split 2-1 for Republicans: roughly 8.5-4.3. This would actually give Republicans a national House vote lead of 49.6-48.9% on Election Day, a Democratic vote decrease of 3.8 points and a loss of 13 House seats (+/-2), very close to the recent median of -15.
Of course, if those undecided voters split evenly, Democrats are back to +3.5; a break toward Democrats seems extremely unlikely. So, let’s split the difference: a Democratic national House vote lead of 1.4 points, which equates to a loss of 6.3 seats, albeit with a 3.1 to 9.5 95% CI, giving Democrats something like a 15-20% chance of retaining their majority. This is as close to a “forecast” as I am willing to come in June 2021.
The bottom line is this: Republicans are favored to win back the House in 2022, though whether extremely narrowly or lopsidedly is far from clear. Historic trends in 1st midterm elections – of which there are only nine since 1960 – suggest Democrats could lose anywhere from 15 to 47 seats. Models with more data points – though still only 26-37 – suggest the shift is likely to be much smaller, anywhere from Democrats essentially holding serve – even netting a seat – to a Republican seat gain in the low double-digits.
Basically, keep an eye on the generic ballot numbers – if they stay close to Democrats ahead 3-4 points, they could be on the verge of defying decades of recent political history. If it drops closer to even, or Republicans pull slightly ahead – it will be a long night for House Democrats on Election Day 2022.
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