Poll bias could erode Democratic midterm advantage, experts caution

A new review of polling data highlights that Democratic advantages in one outlet generic congressional ballot, standing at 49.2 percent to 42.5 percent, may diminish as the November vote draws near. Patrick Ruffini examined over 3,000 Senate polls from the past four cycles and found an average overstatement of Democratic support by 3.7 points, with the bias peaking in July and August before receding. The American Association for Public Opinion Research reported comparable overstatements of Democratic margins in the final two weeks of the 2020 and 2016 elections.

While partisan non-response among occasional voters, particularly those favoring Donald Trump, may inflate Democratic numbers in presidential years, that factor is expected to play a smaller role in the midterms. Recent special-election wins for Democrats in traditionally red states underscore one outlet optimism, yet analysts caution that historical patterns suggest a late-campaign slide toward Republicans. The overall message is that the Democratic lead is not yet secured and could narrow before Election Day.