538's final forecasts for the 2024 election

Through Monday, Nov. 4, 83 million Americans had already cast their ballots in the 2024 election. On Tuesday, Nov. 5 — Election Day — millions more will join them.

Their votes this year will matter more than ever: According to 538’s forecasts for the White House, U.S. Senate and U.S. House, control of the federal government is firmly up for grabs. Our final model runs (published at 6 a.m. Eastern on Nov. 5) give Republicans a roughly 9-in-10 chance of winning control of the Senate, while the House and presidency are both toss-ups. The race for the White House, in fact, may be the closest presidential election in over a century.

Let’s start with the race everyone is watching. According to 538’s final presidential forecast, Vice President Kamala Harris has a 50-in-100 chance of winning the Electoral College after all votes are counted (which could take a few days). We give former President Donald Trump a 49-in-100 chance to win.* Practically speaking, those odds are virtually indistinguishable — about the same as flipping a coin and getting heads versus tails.

Statistically, too, there is no meaningful difference between a 50-in-100 chance and a 49-in-100 chance. Small changes in the available polling data or settings of our model could easily change a 50-in-100 edge to 51-in-100 or 49-in-100. That’s all to say that our overall characterization of the race is more important than the precise probability — or which candidate is technically “ahead.”

More than any other factor, our forecast is so close because the polls are so close. According to our final polling averages, the margin between Trump and Harris is 2.1 percentage points or fewer in all seven swing states. Trump currently leads by 2.1 points in Arizona, 0.9 points in North Carolina, 0.8 points in Georgia and 0.3 points in Nevada. Harris is up by 1.0 point in Wisconsin and in Michigan. And in Pennsylvania (the state that’s most likely to decide the outcome of the election), Harris has a tiny 0.2-point edge.

But it is worth stressing that the polls will not be exactly correct. Polls overestimated Democrats by an average of 3-4 points in both the 2016 and 2020 presidential elections, for example, and overestimated Republicans by an average of 2.5 points in the 2012 presidential election. Our election model expects polls this year to be off by 3.8 points on average, although it could be more or less — and our model thinks this error is equally likely to favor Democrats as Republicans.

In other words, you should not expect polls in presidential races to be perfectly accurate. You should expect them to be as imperfect as they have been historically. And in a race with very narrow advantages for the leader in each key state, that means there’s a wide range of potential outcomes in the election.

And that’s why we’ve been saying the race isn’t necessarily going to be close just because the polls are. Trump and Harris, our model says, are both a normal polling error away from an Electoral College blowout. If we shift the polls by 4 points toward Harris, she would win the election with 319 Electoral College votes:

Meanwhile, Trump would win with 312 electoral votes if the polls underestimate him by the same amount:

ABC News interactive electoral map showing scenario where former President Donald Trump wins all seven key swing states.

ABC News photo illustration

Hopefully, you can see just how uncertain a 50-in-100 chance of winning the election really is. When we say the race for the White House is a toss-up and could go either way, we mean it.

In the 2022 midterm elections, Republicans managed to win back the majority in the U.S. House of Representatives. But they dramatically underperformed historical expectations, especially in seats where their candidates denied the results of the 2020 election. They ended up winning just 222 seats — barely enough to wield a functional majority (and sometimes it wasn’t even that functional).

According to 538’s final House forecast, the Republican Party is in real danger of losing the chamber entirely in 2024. We give them a 49-in-100 chance of controlling the House, while Democrats have a 51-in-100 chance of taking control. But whichever party wins a majority may find it so narrow as to be ungovernable: The median outcome in our forecast is that Democrats win just a one-seat majority.

Yet there is considerable uncertainty here, too. Because House polls are subject to a lot of error, and the other indicators that our House uses can be very noisy, our model thinks there is about a 1-in-2 chance that one party wins a double-digit majority.

To win a double-digit majority, Democrats would have to win all of the seats our model rates as “Likely Democratic,” “Lean Democratic” and “Toss-up” and secure two out of the 23 seats we currently rate as “Lean” or “Likely Republican.” Conversely, Republicans would have to win all of their “Likely” and “Lean” seats, all the “Toss-ups,” and four seats where Democrats are currently favored. Such performances sound ambitious, but it’s common for parties to sweep most or all of the toss-ups when they beat expectations.

One final point on where to expect surprises. We already know that we aren’t going to pick the “right” winners in each seat. That’s by design. Our goal isn’t to pick winners; it’s to correctly estimate probabilities. And for us to succeed in that regard, candidates with a 75-in-100 chance of winning need to win 75 times out of 100 — and lose 25 times out of 100. Our final forecast rates 66 seats as “Toss-up,” “Lean” or “Likely.” Based on how well our model would have predicted similar races in past elections, we expect 14 of those districts to go to the party that’s not favored to win. What’s more, we expect three upsets in districts rated as “Solid” for either party — which means they have at least a 98-in-100 chance of winning.

And now for the race that is decidedly not close: the race to control the Senate. Our model gives Republicans a 92-in-100 chance of winning control of the upper chamber, which includes scenarios in which they win 51 seats or more and scenarios in which they win 50 seats as well as the White House (the vice president breaks ties in the Senate).**

Republicans’ strength in our forecast comes from their expected wins in reliably red Montana and Ohio, where moderate Democratic incumbents are trying to fend off fierce competition from Republicans. In Montana, the GOP has a 93-in-100 chance of defeating Sen. Jon Tester. In Ohio, Sen. Sherrod Brown has a 41-in-100 chance of beating Republican businessman Bernie Moreno. And our forecast gives the Democratic candidate in West Virginia, Glenn Elliott, just a 1-in-1,000 chance of holding onto retiring Sen. Joe Manchin’s seat.

If Democrats lose at least two of these seats, which our forecast reckons should happen about 95 percent of the time, they will need to pick up another seat elsewhere in order to keep their majority. According to our forecast, their best chances of doing so are in Florida or Texas, but they only have a 16-in-100 chance of winning each. That’s not nothing; it’s about the chance of rolling a standard six-sided dice and getting a 1. But it’s still a fairly uphill climb for Democrats.

This is a good time to remind people that our forecasts are not crystal balls. And especially in a year with races this close, they cannot provide more certainty than the data available to us. The point of creating election forecasting models, as I wrote last week, isn't to provide a hyper-accurate, laser-like predictive picture of the election that removes all doubt about what could happen. Rather, it's to give people a good understanding of how the polls could be wrong and what would happen if they are.

In the presidential and House elections, if the polls are off a historically normal amount, either party could come out ahead. In the Senate, the polls would need to be off by more than they were in 2020 in at least one state. That is possible, but given the other information available to us about the seats up for grabs, we think it’s unlikely Democrats will hold the chamber.

*Technically, Harris has a 50.33 percent chance to win and Trump has a 49.45 percent chance to win, and there is a 0.22 percent chance of an Electoral College tie. This is why the rounded numbers appear not to add up to 100 percent.

**As well as scenarios in which Republicans win 50 seats and Nebraska independent candidate Dan Osborn wins his seat and chooses not to caucus with either party.