As of Monday, November 4, 83 million Americans had already voted in the 2024 election. On Tuesday, November 5 – Election Day – they will be joined by millions more.

Their votes this year will matter more than ever: According to 538 predictions for the White House, US Senate and US House, control of the federal government is firmly up for grabs. Our final models (published at 6 a.m. Eastern on Nov. 5) give Republicans about a 9-in-10 chance of winning control of the Senate, while the House and presidency are both up for grabs. The race for the White House, in fact, could be the closest presidential election in over a century.

Presidency

Let’s start with the race everyone is watching. Conformable 538’s final presidential forecastVice President Kamala Harris has a 50-in-100 chance of winning the Electoral College after all the votes are counted (which could take several days). We give former President Donald Trump a 49 out of 100 chance of winning.* Practically speaking, these odds are virtually indistinguishable – much like flipping a coin and getting heads versus tails.

Statistically, too, there is no significant difference between a 50 in 100 chance and a 49 in 100 chance. Small changes to the available data or polling settings of our model could easily change a 50 in 100 advantage to a 51 in 100 or 49 in 100. That means our overall characterization of the race is more important than the exact probability — or which candidate is technically “in front.”

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 less 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 1.0 points in Wisconsin and Michigan. And in Pennsylvania (the state most likely to decide the outcome of the election), Harris has a slim lead of 0.2 points.

But it’s worth pointing out that polls won’t be exactly fair. 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 presidential election since 2012. Our election model expects this year’s polls to drop by an average of 3.8 points, though it could be more or less — and our model thinks that this error is just as likely to favor Democrats as well as Republicans.

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

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

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

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

House of Representatives

In the 2022 midterm elections, Republicans managed to regain their majority in the US House of Representatives. But they dramatically underperformed historical expectations, especially in places where their candidates negated the 2020 election results. They ended up winning just 222 seats—barely enough to hold a workable majority (and sometimes it wasn’t even that workable). .

According to the final House 538 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 average result in our forecast is Democrats winning only a one-seat majority.

However, there is considerable uncertainty here as well. Because House polls are subject to a lot of error, and the other indicators our House uses can be very noisy, our model estimates that there is about a 1 in 2 chance that a party will win a double-digit majority.

To win a double-digit majority, Democrats would need to win all seats that our model considers “Likely Democratic,” “Lean Democratic,” and “Toss-up,” and secure two of the 23 seats that we currently rate them as “Lean”. ” or “Probably Republican.” Conversely, Republicans should win all of their “likely” and “throwback” seats, all of their “throwback” seats, and four seats where Democrats are currently favored. Such performances sound ambitious, but it is common for parties to sweep most or all of the throws when they exceed expectations.

One last point about where to expect surprises. We already know we’re not going to pick the “right” winners at every venue. That’s by design. Our goal is not to pick winners; is to correctly estimate the probabilities. And for us to succeed in this regard, candidates with a 75 out of 100 chance of winning must win 75 times out of 100 – and lose 25 times out of 100. Our final forecast rates 66 seats as “Tosses” . “Weak” or “Probable”. Based on how well our model would have predicted similar races in past elections, we expect 14 of these districts to go to the non-favored party to win. Additionally, we expect three upsets in districts rated “Solid” for either side — meaning they have at least a 98-out-of-100 chance of winning.

Senate

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

Republican strength in our forecast comes from expected wins in Montana and safe-red Ohio, where incumbent moderate Democrats are trying to avoid stiff 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 defeating Republican businessman Bernie Moreno. And our forecast gives West Virginia Democratic candidate Glenn Elliott just a 1-in-1,000 chance of retaining retiring Sen. Joe Manchin’s seat.

If Democrats lose at least two of those seats, which they estimate should happen about 95 percent of the time, they will have to pick up another seat elsewhere to keep their majority. According to our forecast, the best odds of doing so are in Florida or Texas, but they only have a 16-in-100 chance of winning each. This is nothing; it’s about the chance of rolling a standard six-sided die and getting a 1. But it’s still quite an uphill climb for the Democrats.

Our last word

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

In the presidential and parliamentary elections, if the polls are not historically normal, either party could come out on top. In the Senate, polls should be more off than they were in 2020 in at least one state. It’s possible, but given the other information available about the seats at stake, we think it’s unlikely that the Democrats will hold the chamber.

Footnotes

*Technically Harris has a 50.33% chance of winning and Trump has a 49.45% chance of winning and there is a 0.22% chance of an Electoral College tie. This is why the rounded numbers don’t seem to add up to 100 percent.

**Same as scenarios where Republicans win 50 seats and Nebraska independent Dan Osborn wins his seat and chooses to run with no party.