Election Day is tomorrow, and while there are high expectations for Democrats, it’s impossible to know for certain what will happen in the race for control of Congress.

Many Democrats are worried about the polls overestimating the strength of their candidates again, while President Donald Trump and some in the GOP seem sanguine in the final days.

So, what if Republicans overperform or even keep their majorities? And what if Democrats have a historic midterm? Let’s break down how each of those scenarios could happen.

The polls were wrong A Kansas Senate poll released by The Washington Post on Friday epitomized the nightmare scenario for Democrats: that polls — especially in red states — could systematically underestimate Republicans because they don’t respond to them as much.

This “nonresponse bias” led to polls being off in the 2016 and 2020 presidential elections. It hasn’t been seen as much in the midterms in the Trump era, but that doesn’t mean it couldn’t happen. And given Democrats are chasing a lot of red territory, this would likely take a big chunk out of their gains.

The Senate map was just so red Consider this: Even if the margins of the 2024 vote uniformly shifted toward Democrats by 10 points in every state, Democrats would still get to only 49 Senate seats. In other words, they could notch one of the biggest popular-vote victories in decades and still not win the Senate because this year’s battlefield is overwhelmingly made up of Trump states.

Democrats need a net gain of four seats, which requires them flipping at least two states that Trump won by double digits. (To underscore the difficulty of the playing field for Democrats, they are on offense in only one state where Kamala Harris won in 2024.) The GOP pulled an upset in Maine and/or Michigan The number of GOP Senate seats Democrats need to pick off increases if they lose the ones they’re defending — namely Maine, Michigan or both. Democrats probably should have put those away by now, but haven’t — in part thanks to Democratic Senate nominees who aren’t running as well as the gubernatorial nominees in the same state.

The GOP’s gerrymandering was too successful It’s conventional wisdom that the House very likely flips to Democrats. But if Republicans pull the unthinkable and keep their majority — or even just keep Democrats’ gains to a minimum — the GOP’s brazen mid-decade gerrymandering push will likely have played a role. The effort, which Democrats weren’t able to match because they lack as much control in state governments, will have allowed Republicans to win as many as nine additional seats. They surely won’t win all of those, but the creation of those safer GOP seats raised the bar for Democrats.

Voters didn’t care much about the Iran war, corruption and other unpopular Trump ideas So much of what Trump has done has been unpopular — often by large margins. But if Republicans do better than expected, a big reason might be that voters didn’t care enough about Trump’s actions for them to matter.

Maybe they think his White House ballroom and efforts to glorify and enrich himself are gauche, but that behavior isn’t as important to Trump’s base as culture wars and opposing Democrats. Maybe they don’t like the Iran war, but since it’s not a conventional ground war with many US troop deaths, it’s not as front of mind.

Trump’s historic unpopularity By many measures, Trump is the most unpopular president in modern history heading into a midterm. He’s 30 points underwater in the CNN Poll of Polls, with 34% approving of his job performance and 64% disapproving. And Trump is so ever-present that it’s nearly impossible for Republicans to distance themselves from him. It’s simply very difficult to win elections — no matter how favorable the Senate map is to Republicans — when people dislike the face of the GOP by a nearly 2-to-1 margin.

Trump’s coalition broke down Trump swept the swing states in the 2024 election in large part by making big gains with young people (especially men), Latinos and infrequent voters. But the polls suggest all three groups have turned sharply against him. And it’s not just that; his tariffs and the Iran war appear to have damaged Trump’s standing with his most reliable and consistent demographic: White voters without college degrees. The GOP hoped Trump was building a lasting new coalition. But it hasn’t turned out when he hasn’t been on the ballot, and now it might desert the GOP.

Trump’s neglect of affordability Trump’s cardinal political sin might have been his utter neglect of what almost always polls as voters’ chief concern: affordability. He was elected in large part because of high inflation under former President Joe Biden and his own promises to fix it quickly.

But Trump not only launched policies that exacerbated economic problems — a recent New York Federal Reserve study found the overall cost of consumer goods would have fallen without his tariffs — he also called affordability a “hoax” and falsely claimed he had fixed the problem. Polls showed Americans never bought that, though. Around three-quarters said he and his administration hadn’t focused enough on affordability. And more Americans blame Trump for economic problems than ever blamed Biden.

Broken promises Related to the two preceding items is that Trump simply didn’t do the things he promised. He said he wasn’t going to start wars, but he did. He said he was going to fix inflation, and it’s now worse. A recent AP-NORC poll found that 54% of Americans said Trump didn’t try to keep his promises. And even among those who said he did try, more said he had failed to actually keep them (28%) than said he kept them (17%). That’s 8 in 10 Americans who said he’s failed to keep his promises.

Podcaster Joe Rogan, who backed Trump in 2024, has been big on this. It’s one thing to break promises when the economy is good (as Trump did in his first term); it’s another to break them on voters’ central issue.

The GOP mobilized non-White voters — in the wrong way Perhaps no demographic has swung against Trump by as much as Latino voters. That’s in part thanks to his economic policies, but also a mass-deportation effort that is widely seen as overzealous. There is also some evidence that the Supreme Court further weakening the Voting Rights Act and Republicans gutting heavily Black congressional districts could be mobilizing Black voters.

That demographic, especially, could play a major role in Senate races that Democrats are targeting such as in Florida, Mississippi, Ohio and South Carolina, as well as those they’re defending like in Michigan.

has emerged as a major concern for Americans — sometimes even polling above prices. But more significantly, there is growing evidence that voters’ concerns about corruption are more of a problem for Republicans than Democrats, perhaps because of a spate of headlines about Trump’s self-enrichment and members of his administration apparently leveraging their positions for financial gain. CNN and New York Times/Siena polls have shown Democrats leading Republicans on the issue by 7 and 11 points, respectively.

And a CBS News poll showed 52% of Americans said corruption would increase if Republicans win the midterms versus just 37% who said the same if Democrats won.