Election Polls Got The Midterm Winner Right. But They Missed The Scale Of The Democratic Victory.

Pollsters correctly predicted a big Democratic win in Tuesday's midterm elections. What didn't anticipate, however, was the sheer scale of the Republican defeat.

An early analysis of the national House popular vote puts the Democrats' lead at around 13 percentage points, well ahead of the 8.8-point margin in the final Silver Bulletin polling average. The gap is striking, considering the changes polling firms have made over the past decade to improve their election forecasts.

The estimate comes from Lakshya Jain, an election analyst at The Argument, who examined the results Wednesday. His assessment suggests that the final polling average underestimated Democratic support relative to Republican support by more than four points.

The national vote count is still incomplete, so that margin could change. But the preliminary figures indicate a polling miss comparable in size to the one recorded in 2020, when surveys considerably overestimated Democratic support.

In 2016, 2020 and 2024, pollsters repeatedly struggled to account for voters who supported Donald Trump. While national surveys were relatively close in 2016, some battleground-state polls badly underestimated his strength. The problem was even more pronounced in 2020, when polling errors reached levels not seen in decades.

The industry responded by changing how it conducts and adjusts surveys, particularly when estimating the political preferences of people who are difficult to reach.

One increasingly common practice is to weight survey results using respondents' party affiliation or how they voted in previous elections. The idea is to prevent a sample containing too many Democrats or too few Republicans from producing a misleading picture of the electorate.

A September study from Pew Research Center found that almost 70% of national polls used some form of political weighting in 2024. Pew's analysis showed that such adjustments generally improved accuracy, particularly because Republicans have become somewhat less likely than Democrats to participate in surveys.

But there is a complication. A poll adjusted to reflect how Americans voted in 2024 might not accurately capture an electorate that looks very different two years later.

Republicans who turned out for Trump in the presidential election may have been less motivated to vote this time, while some former Trump supporters may have switched to Democrats. A survey that relies too heavily on previous voting behavior could miss those changes.

Pew itself has warned that weighting surveys against outdated measures of party affiliation can introduce errors. Its research also makes clear that weighting generally improves accuracy, rather than causing polling mistakes.

The midterm results have therefore raised a question about whether polling firms overcompensated for their previous tendency to underestimate Republicans. Establishing that would require a closer examination of how individual surveys were conducted, including their turnout models and weighting methods.

Some pollsters, though, came remarkably close to predicting the Democratic margin. AtlasIntel conducted its final national survey between Oct. 28 and Nov. 1, interviewing 3,566 respondents. It found 55.5% supporting Democratic candidates for the House and 41.4% backing Republicans, giving Democrats a 14.1-point lead.

That was substantially higher than the final Silver Bulletin average and much closer to the early estimate of the actual national House vote.

AtlasIntel subsequently ranked its own survey first among the final national House polls, using a projected Democratic margin of 13.8 points. By that measure, its estimate was off by just 0.3 points.

The ranking is the firm's own assessment, and the final vote margin has not yet been established. Still, AtlasIntel's pre-election numbers were notably closer to the preliminary result than those of several other major surveys.

For comparison, the final Focaldata-Financial Times poll, released November 2, gave Democrats a 7.4-point lead among likely voters. That was roughly half the margin projected by AtlasIntel, despite both surveys being conducted in the closing days of the campaign.

Silver Bulletin's final average put Democrats at 51.8% and Republicans at 43%, a lead that comfortably anticipated the direction of the election without capturing its full magnitude.