Can the polls be trusted? It depends on what you’re trusting them to do. Even the most carefully conducted polls are imprecise snapshots of public opinion, not precision instruments — and when they’re pressed into predictive tools, they don’t always get it right. But while surveys can’t provide an unambiguous answer on who’s ahead in tight races, they often do paint a clear and important picture of the political landscape.

The contours of some findings are sharply drawn enough to be visible even through the shadows of potential polling error. Poll after poll has found President Donald Trump’s approval rating in the mid-to-low-30s nationally. Surveys also show a broad consensus that Americans, shaken by cost of living concerns, largely take a dim view of the economy and Trump’s stewardship of it; that there’s little enthusiasm in any corner about the current state of the nation; and that voters are overwhelmingly looking for change — even if they may not all agree on precisely what that change should look like.

Similarly, Democrats’ lead on the national “generic ballot” has been consistent and robust enough to suggest that the party has an overall advantage — and it would require an unprecedented level of polling error to overcome that. But there’s far less certainty about the precise level of that advantage, or how that might play out in individual races. Even a small difference in Democratic strength compared to what the polls suggest could mean the difference between a blue wave that sweeps well into Republican territory, and one that fails to overcome a deeply Republican-friendly Senate map.

One thing that’s challenging for pollsters this year is that there’s another finding that looks simultaneously like a defining factor of the race and a potential source of polling error: the yawning gap in partisan enthusiasm about voting.

Polls — consistent with early voting data — have found that, compared to Republicans, Democrats report being far more motivated to vote this year. That’s playing a role both in pollsters’ efforts to get people to answer surveys, and in their attempts to identify which potential voters will actually end up casting ballots in this election.

Per Gallup, the Democratic enthusiasm advantage is the largest in any midterm dating back to 1994. That’s in part because, particularly in his second term, Trump provokes far more fervent opposition than he does ardent support. It also owes in part to the growing education divide in American politics, with college-educated voters likelier than those without degrees both to turn out in a midterm year, and to vote Democratic if they do. But that same enthusiasm divide could also be shaping voters’ willingness to respond to polls.

In a Washington Post-Schar School poll of Kansas, for instance, registered Democrats who were contacted by interviewers were far likelier than registered Republicans to complete the survey. While that disparity hasn’t been universal this cycle, the final set of New York Times/Siena College polls also saw a similar response pattern.

This type of variation, sometimes called “differential nonresponse,” isn’t an entirely new challenge for pollsters. Some types of people have always been more likely than others to answer surveys, including older adults, those with higher levels of education and those who are more civically engaged. Pollsters address that disparity by weighting their results to make the demographics of their sample look more like the broad universe of people they’re trying to measure. Increasingly, that also includes weighting to known partisan targets, such as the levels of party registration in a state or vote choice in the 2024 election.

What concerns pollsters are those patterns that aren’t fully corrected for, even after weighting to demographic and partisan targets. A poll could have the “right” number of Republicans and Democrats to reflect the electorate but not reach the right mix of voters within each party.

Not every registered voter turns out to cast a ballot in each election — in most years, 40% or more sit it out — and that can also complicate the picture for pollsters. In order to reflect the views of those who do ultimately turn out, pollsters identify likely voters, and those efforts can be complicated by the same factors that make it hard to reach less enthused potential voters.

There’s a possibility that some types of Republicans may be too disengaged to respond to surveys, but still sufficiently motivated that they’ll end up voting — or that the most engaged and enthusiastic Democrats will be overrepresented in surveys.

Even if the polls accurately reflect the dynamics at the time they were conducted, there’s still room for a shift after that polling is completed if Republican voters coalesce late around their candidates.

CNN’s final state polls, for instance, gave voters an option to say they wouldn’t support either candidate in the upcoming Senate race — and even after being asked a follow-up question about which way they’d lean, 6% to 8% in each poll said that, between the two leading candidates, they’d back “neither” or someone else. The poll also pressed voters to choose which party they’d rather see in control of the Senate, even if they initially said it didn’t matter to them.

Looking at those two questions together tells us that in most of these polls, voters who favor GOP control were more likely than those who’d rather see a Democratic win to opt out of picking a major-party candidate — by about 9 points in Texas, 6 points in Kansas and 4 points in Michigan.

That could well reflect what happens on Election Day. The Republican nominees in Texas and Kansas, Ken Paxton and Roger Marshall, face specific image problems that have made it more difficult for them to consolidate their party’s support, and it’s fully plausible that GOP-inclined voters in those states might end up taking a pass on the race altogether. But it also suggests that Democrats haven’t yet sealed the deal. In a set of relatively tight races, that could be enough to significantly tighten margins or change the outcome of some races altogether.

On the other hand, it’s not a given that any polling miss would be in favor of the Democrats. Presidential polls in the past three cycles have underestimated Republicans’ share of the vote relative to Democrats: by around 3 points in 2016 and 2024, and close to 5 points in 2020.

But there hasn’t been a similar pattern in Trump-era midterm elections. Nor is it guaranteed that polling misses would look the same across the many different states in play.

As we wrote in 2024, polling data is a single, imperfect gauge of people’s opinions. But polls of the US, ultimately, are a means of talking to Americans across a wide range of demographics, life experiences and views, on topics that stretch far beyond elections, or even politics. In a deeply fragmented society, and with social media often reflecting an unrepresentative sample of the loudest voices, they’re still a valuable tool for understanding the country as a whole.