In 2016, Clinton’s lead over Trump in the final seven days of polling averaged 2.5 percentage points (or those polls covered by RealClearPolitics (RCP). Clinton’s edge in the nationwide tally of popular votes was 2.1 percentage points. Despite her (meaningless) nationwide edge, she lost to Trump because he won Michigan, Pennsylvania, and Wisconsin — each by less than 1 percentage point. Those states’ 46 electoral votes gave Trump the win over Clinton.
In 2020, Biden’s lead over Trump in the final seven days of polling averaged 7.9 percentage points for those polls covered by RCP. Biden’s edge in the nationwide tally of popular votes was 4.5 percentage points; that is, slightly below the bottom of the 95-percent confidence interval around the apparent 7.9-point lead. Despite his (meaningless) 4.5-point lead in the popular vote, Biden won the election only because he edged out Trump in both Georgia and Wisconsin by less that 1 percentage point and in Pennsylvania by a little more than 1 percentage point. Those states’ electoral votes gave Biden his win over Trump.
Hypothesis: Clinton and Biden underperformed at the ballot box vs. their poll numbers because the polls (on average) were biased somewhat toward Clinton in 2016 and much more so toward Biden in 2020. This hypothesis is supported by a report issued by the American Association for Public Opinion Research (https://aapor.org/wp-content/uploads/2022/11/AAPOR-Task-Force-on-2020-Pre-Election-Polling_Report-FNL.pdf):
● The 2020 polls featured polling error of an unusual magnitude: It was the highest in 40 years for the national popular vote….
● The polling error was much more likely to favor Biden over Trump. Among polls conducted in the last two weeks before the election, the average signed error on the vote margin was too favorable for Biden by 3.9 percentage points in the national polls and by 4.3 percentage points in statewide presidential polls.
● The polling error for the presidential election was stable throughout the campaign. The average error matched closely for polls conducted in the last two weeks, in the final week, and even in the final three days. The challenges polls faced in 2020 did not diminish as Election Day approached.
● Beyond the margin, the average topline support for Trump in the polls understated Trump’s share in the certified vote by 3.3 percentage points and overstated Biden’s share in the certified vote by 1.0 percentage point. When undecided voters are excluded from the base, the two-candidate support in the polls understated Trump’s certified vote share by 1.4 percentage points and overstated Biden’s vote share by 3.1 percentage points.
The report also concludes that the bias wasn’t due to the massive surge in early voting and mail-in voting in 2020.
The foregoing suggests that if the polls remain strongly biased toward Biden in 2024, and if he polls much worse than he did in 2020, his candidacy is doomed.
With that background, I refer you to the following graph, which compares results of polls reported by RCP for the elections of 2016, 2020, and 2024. The results represent polls conducted between June 1 and election day of each election year. We’re a long way from election day 2024, but the results to date are ominous for Biden; he is running behind Clinton’s losing pace of 2016. Stay tuned.
Politics and Prosperity 