With the midterm elections just weeks away, pollsters are fine-tuning their models to forecast which party will control Congress. Both the House and Senate are genuinely competitive, and the president's frequent, often contradictory statements add another layer of unpredictability to an already volatile political environment. As a result, even the most sophisticated polling operations are bracing for the possibility of significant error—this time, for reasons that go beyond traditional sampling challenges.
Polling fundamentally relies on asking a small sample of voters to project the behavior of the entire electorate. But four distinct problems make that projection increasingly unreliable. First, pollsters must determine whether respondents are registered to vote. Second, they must gauge the likelihood that those respondents will actually cast a ballot. Third, they ask about candidate preferences or expected winners. And fourth—the factor over which pollsters have the least control—is the gap between stated intention and real-world behavior at the ballot box, including deliberate non-voting or leaving certain races blank.
Recognizing that direct questions often yield misleading answers, pollsters now use a series of indirect questions designed to reveal underlying behavioral patterns. Yet even with larger sample sizes, they cannot fully correct for hidden biases or mismatches between the people surveyed and those who actually show up. The core challenge remains: aligning the sample with the electorate that materializes on Election Day.
Current forecasts show Democrats favored to retake the House, and their odds of also winning the Senate have improved dramatically in recent months. The House prediction is unsurprising given the Republicans' razor-thin majority, even after the 2025 redistricting that largely protected GOP incumbents. The Senate shift, however, was nearly unthinkable just a few months ago. Some Republican strategists still hope to hold both chambers, but with a historically unpopular president urging voters to treat the midterms as a referendum on him, those hopes are fading. As trust in election counts erodes, the uncertainty only deepens.
The historical pattern is stark: since the 1970s, only two presidents—Bill Clinton in 1998 and George W. Bush in 2002—have seen their party gain House seats in a midterm. In 2018, during Trump's first term, Democrats picked up 41 House seats. That same headwind is expected to blow again this year, and it may be even stronger given the current president's approval ratings. Indeed, half of Democratic voters expect a sweep, citing Trump as the catalyst.
Yet the most consequential factor may be what happens inside the voting booth—or outside it. The group that will determine the size of Democratic gains is not registered Democrats (who will vote Democratic) or independents (who are already leaning more Democratic than in past cycles). The wildcard is Republican voters, particularly non-MAGA Republicans and Latino voters in states like Texas, who are unhappy with rising gasoline prices, the affordability crisis, and the aggressive immigration enforcement by ICE. Many will still vote Republican, but a significant faction may simply stay home or leave the top of the ticket blank. In close races, that passive protest effectively becomes a vote for the Democratic candidate.
Midterm turnout is traditionally lower than presidential years, and this cycle is likely to follow that trend—though an unpopular president may energize opposition voters. The combination of low turnout and a disaffected Republican base could produce a Democratic wave that polls, which historically undercount such dynamics, may not fully capture.
Prediction markets, which aggregate betting on election outcomes, are already pointing to Democratic victories across the board. But pollsters and market analysts alike acknowledge that the gap between what voters say and what they do on Election Day remains the great unknown. As legal battles over voter rolls and ICE's review of voter registration groups add further complications, the 2027-2028 Congress may well be decided not by the ballots cast, but by the ones left uncast.
