2020 Iowa Caucuses: How did my polling averages fare?

Given the extremely volatile polling for the 2020 Democratic presidential nomination following the conclusion of the Iowa Caucuses, I will not provide global monthly updates for next few months. Instead, I will focus on the first handful of primaries and caucuses: Iowa on February 3, New Hampshire on February 11, Nevada on February 22, South Carolina on February 20, the 14 Super Tuesday contests on March 3, and so forth.

Also: I now weight polls conducted partially after February 3, 2020 either 1.333 or 1.667 times higher, and polls conducted entirely after February two times higher, than polls conducted entirely before February 4, 2020.

On the night of February 3, 2020, I was sitting on my usual spot on our sofa, watching MSNBC and anticipating returns from that day’s Iowa Caucuses.

Iowa Visitor Center Sep 1990

Earlier that day, I had published my final WAPA (weighted-adjusted polling average) for the 11 declared Democratic presidential candidates, calculated four different ways (Table 1):

  • Using all 58 polls conducted since January 1, 2019
  • Using only the 45 polls released since the 1st Democratic debate on June 26, 2019
  • Using only the 21 polls released since the 5th Democratic debate on November 19, 2019
  • Using only the 15 polls released since the 7th Democratic debate on January 14, 2020

Table 1: Final Iowa Caucuses WAPA for declared 2020 Democratic presidential nomination candidates

Candidate All Polls Since 1st Debate Since 5th Debate Since 7th Debate
Biden 19.9 19.8 20.1 20.3
Sanders 18.4 18.8 21.0 22.7
Warren 17.1 18.1 15.6 15.6
Buttigieg 15.9 16.8 16.7 16.7
Klobuchar 6.9 7.3 9.1 9.7
Yang 3.0 3.2 3.6 3.9
Steyer 2.8 3.1 3.1 3.5
Gabbard 1.5 1.6 1.5 1.6
Bloomberg 0.4 0.4 0.6 0.5
Bennet 0.3 0.3 0.2 0.3
Patrick 0.0 0.0 0.0 0.1
DK/Other 13.8 10.6 8.5 5.2

Based solely on these numbers, one would reasonably draw the following conclusions:

  • United States Senator (“Senator”) from Vermont Bernie Sanders and Minnesota Senator Amy Klobuchar were rising in the polls heading into the Iowa Caucuses, as to a lesser extent were entrepreneur Andrew Yang and businessman Tom Steyer.
  • Massachusetts Senator Elizabeth Warren was declining in the polls.
  • No other candidate was moving in the polls one way or the other.

By 11:37 pm EST, however, I had grown tired of waiting for results other than successive waves of entrance polls, so I tweeted the following:

RIP, Iowa Caucuses (1972-2020)

I have defended their idiosyncrasies for decades, believing the retail aspects of campaigning there outweighed the low-turnout mischegoss of the process.

 No more.

 This is ridiculous.

 #IowaCaucuses #iowacaucus2020

I will not relitigate here the myriad problems the Iowa Democratic Party had with tabulating, validating and releasing three distinct measures:

  1. Initial headcount of support for each Democratic candidate (“Initial tally”)
  2. Post-realignment headcount of support for each Democratic candidate (“Final tally”)
  3. Allocation of “state delegate equivalents,” or SDE’s, the only measure ever previously reported

Moreover, my annoyance has abated since Monday night, primarily because I suspect these vote-reporting snafus revealed that the byzantine process of converting persons standing in rooms, then possibly standing in different parts of the room, into SDE’s has always been “riddled with errors and inconsistencies,” to quote a recent New York Times headline. And if this marks the beginning of the end of using caucuses to allocate delegates to each party’s nominating conventions, so be it; they are undemocratic, exclusionary and overly complex.

As for which states “should” come first in future presidential nominating processes, I am currently agnostic.

Three days later, we finally have near-final results from the Iowa Caucuses (Table 2):

Table 2: Near-final Iowa Democratic Caucuses results, February 3, 2020

Candidate Initial Tally Final Tally SDE’s
Biden 15.0 13.7 15.8
Sanders 24.8 26.6 26.1
Warren 18.4 20.2 18.0
Buttigieg 21.3 25.0 26.2
Klobuchar 12.7 12.3 12.3
Yang 5.0 1.0 1.0
Steyer 1.7 0.2 0.3
Gabbard 0.2 0.0 0.0
Bloomberg 0.1 0.0 0.0
Bennet 0.1 0.0 0.0
Patrick 0.0 0.0 0.0
Uncommitted 0.6 0.1 0.2

The following three tables list the arithmetic differences between each candidate’s final Iowa Caucuses WAPA and each of the three reported measures; positive values indicate better performance in the Caucuses than in the polls.

Table 3: Arithmetic difference between Initial Iowa Caucuses % of vote and Iowa Caucuses WAPA

Candidate All Polls Since 1st Debate Since 5th Debate Since 7th Debate Mean

Difference

Biden -4.9 -4.8 -5.1 -5.3 -5.0
Sanders 6.4 6.0 3.8 2.1 4.6
Warren 1.3 0.3 2.8 2.8 1.8
Buttigieg 5.4 4.5 4.6 4.6 4.8
Klobuchar 5.8 5.4 3.6 3.0 4.5
Yang 2.0 1.8 1.4 1.1 1.6
Steyer -1.1 -1.4 -1.4 -1.8 -1.4
Gabbard -1.3 -1.4 -1.3 -1.4 -1.4
Bloomberg -0.3 -0.3 -0.5 -0.4 -0.4
Bennet -0.2 -0.2 -0.1 -0.2 -0.2
Patrick 0.0 0.0 0.0 -0.1 0.0
DK/Other -13.2 -10.0 -7.9 -4.6 -8.9

Initial tally. If the Iowa Caucuses were instead the Iowa Primary, this would have been the only vote reported. On this measure Sanders, Klobuchar and former South Bend, IN Mayor Pete Buttigieg averaged 4.5-4.8 percentage points (“points”) higher in the initial tally than in their WAPA. And the closer in time the polls were to the Iowa Caucuses, the more “accurate” the WAPA.

Warren (+1.8 points) and Yang (+1.6) also overperformed their WAPA in the initial tally, albeit by smaller margins. And for Warren, older polls were more predictive than recent polls.

By contrast, former Vice President Joe Biden did an average of 5.0 points worse in the initial Iowa Caucuses tally than his WAPA. Steyer and United House of Representatives Member from Hawaii Tulsi Gabbard (-1.4 each) also performed somewhat worse than their WAPA.

Table 4: Arithmetic difference between Final Iowa Caucuses % of vote and Iowa Caucuses WAPA

Candidate All Polls Since 1st Debate Since 5th Debate Since 7th Debate Mean

Difference

Biden -6.2 -6.1 -6.4 -6.6 -6.3
Sanders 8.2 7.8 5.6 3.9 6.4
Warren 3.1 2.1 4.6 4.6 3.6
Buttigieg 9.1 8.2 8.3 8.3 8.5
Klobuchar 5.4 5.0 3.2 2.6 4.1
Yang -2.0 -2.2 -2.6 -2.9 -2.4
Steyer -2.6 -2.9 -2.9 -3.3 -2.9
Gabbard -1.5 -1.6 -1.5 -1.6 -1.6
Bloomberg -0.4 -0.4 -0.6 -0.5 -0.5
Bennet -0.3 -0.3 -0.2 -0.3 -0.3
Patrick 0.0 0.0 0.0 -0.1 0.0
DK/Other -13.7 -10.5 -8.4 -5.1 -9.4

Final tally. Only three candidates improved their vote totals after supporters of non-viable candidates shifted to a viable candidate (15% of attendees at a precinct caucus):

  • Buttigieg (+5,638 supporters; +3.7 points)
  • Warren (+2,238; +1.8)
  • Sanders (+2,155; +1.8)

These three candidates, as well as Klobuchar (-1,288; -0.4), performed better in the final tally than their WAPA, on average. As with the initial tally, WAPA using more recent polls was most predictive for Sanders, Buttigieg and Klobuchar, while WAPA using older polls was most predictive for Warren.

Biden, on the other hand, lost 2,693 supporters and dropped 1.3 points between the initial and final tallies; Yang and Steyer also lost considerable support between the initial and final tallies. For all three candidates, WAPA using earlier polls was most predictive.

Table 5: Arithmetic difference between Iowa Caucuses SDE % and Iowa Caucuses WAPA

Candidate All Polls Since 1st Debate Since 5th Debate Since 7th Debate Mean

Difference

Biden -4.1 -4.0 -4.3 -4.5 -4.2
Sanders 7.7 7.3 5.1 3.4 5.9
Warren 0.9 -0.1 2.4 2.4 1.4
Buttigieg 10.3 9.4 9.5 9.5 9.7
Klobuchar 5.4 5.0 3.2 2.6 4.1
Yang -2.0 -2.2 -2.6 -2.9 -2.4
Steyer -2.5 -2.8 -2.8 -3.2 -2.8
Gabbard -1.5 -1.6 -1.5 -1.6 -1.6
Bloomberg -0.4 -0.4 -0.6 -0.5 -0.5
Bennet -0.3 -0.3 -0.2 -0.3 -0.3
Patrick 0.0 0.0 0.0 -0.1 0.0
DK/Other -13.6 -10.4 -8.3 -5.0 -9.3

SDEs. The same pattern holds for SDEs as for final vote tally, with one minor modification.

  • Buttigieg, Sanders and Klobuchar outperformed their WAPA, with the difference decreasing with more recent polls
  • Warren outperformed her WAPA, with the difference increasing with more recent polls
  • Biden, Steyer and Yang underperformed their WAPA, with the difference increasing with more recent polls.

The bottom line. To evaluate these comparisons globally, I used the sum of the squared differences (“SSE”) between each WAPA value and the results value. Excluding “DK/Other,” Table 6 lists the SSE for each comparison; higher values indicate lower predictive power.

Polling period Initial Tally Final Tally SDEs
All Polls 136.5 240.5 224.9
Since 1st Debate 115.8 210.8 198.2
Since 5th Debate 88.3 190.4 168.0
Since 7th Debate 77.1 177.8 156.1

WAPA was most predictive of the initial tally, not surprising given that poll respondents are asked which candidate they planned to support upon arriving at the caucus site, and not about second or third choices. WAPA was also slightly more predictive of the distribution of SDEs than of the final raw tally of supporters, though neither was especially predictive.

For each reported measure, WAPA was more predictive the closer the polls were to the Caucuses; I will admit this rather surprised me, given the candidate-specific differences detailed above. One explanation is that including older polls, however low-weighted, masks late polling movement of the kind that occurred to Sanders, Buttigieg and Klobuchar.

For now, however, I will continue to report multiple versions of WAPA, if only to see if this pattern holds for later contests.

Now, on to New Hampshire!

Until next time…

6 thoughts on “2020 Iowa Caucuses: How did my polling averages fare?

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