Until Monday November 4 83 million Americans had already voted in the 2024 elections. On Tuesday, November 5 – election day – millions more will join them.

Their votes this year will count more than ever: According to 538 forecasts for the White House, U.S. Senate and House of Representatives, control of the federal government is definitely in play. Our final model (released at 6 a.m. PDT Eastern on November 5) gives Republicans about a 9 in 10 chance of taking control of the Senate, while the House and presidency are both neck and neck. The race for the White House, in fact, may well be the closest presidential election in over a century.

The presidency

Let’s start with the race that everyone is watching. According to Final presidential forecast of 538Vice President Kamala Harris has a 50/100 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 out of 100 chance of winning.* In practice, those odds are virtually indistinguishable – pretty much like flipping a coin and getting tails.

Also statistically, there is no significant difference between a 50 in 100 chance and a 49 in 100 chance. Small changes in the available polling data or in our model parameters could easily change an edge of 50 out of 100 in 51 out of 100 or 49 out of 100. All of this is 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 forecasts are so close because the polls are so close. According to our latest 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 Arizona0.9 points in North Carolina0.8 points in Georgia and 0.3 points in Nevada. Harris is up 1.0 points in Wisconsin and in Michigan. And in Pennsylvania (the state which is most likely to decide the outcome of the election), Harris has a small advantage of 0.2 points.

But it should be emphasized that the polls won’t be entirely accurate. Polls overestimated Democrats by 3 to 4 points on average in the 2016 and 2020 presidential elections, for example, and overestimated Republicans by 2.5 points on average in the 2012 presidential election. Our electoral model This year expects an error of 3.8 points on average, although it could be more or less – and our model thinks this error is just as likely to favor Democrats as Republicans.

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

And that’s why we say the race won’t necessarily be close just because the polls are. Trump and Harris, our model says: are both a normal polling error, far from an Electoral College blowout. If we shift the polls by 4 points in favor of Harris, she would win the election with 319 Electoral College votes:

Meanwhile, Trump would win with 312 electoral votes if the polls underestimate him that much:

I hope you understand how uncertain a 50/100 chance of winning the election is. When we say the race for the White House is a draw and could go either way, we mean it.

The House of Representatives

In the 2022 midterm elections, Republicans managed to regain the majority in the US House of Representatives. But they Significantly underperforming historical expectationsparticularly in seats where their candidates denied the 2020 election results. They ultimately won only 222 seats – barely enough to hold a functional majority (and sometimes that wasn’t even that functional).

According to Final forecast of 538 for the HouseThe Republican Party is in real danger of losing the House completely in 2024. We give them a 49/100 chance of controlling the House, while Democrats have a 51/100 chance of taking control. But whichever party wins a majority, it may be so narrow as to be ungovernable: the median outcome of our forecast is that Democrats will only get a one-seat majority.

But here too there is considerable uncertainty. Since House polls are subject to many errors and other indicators used by our House can be very noisy, our model estimates that there is about a 50/50 chance that one party will win a two-person majority numbers.

To win a double-digit majority, Democrats would need to win all the seats our model rates as “likely Democratic,” “lean Democratic,” and “toss-up” and win two of the 23 seats we currently rate as “lean.” » or “Probably Republican”. Conversely, Republicans are projected to win all of their “likely” and “skinny” seats, all of the “toss-ups,” and four seats where Democrats are currently favored. Such performances seem ambitious, but it is common for parties to win most or all of the draws when they exceed expectations.

One last point about knowing where to expect surprises. We already know that we’re not going to pick the “right” winners in every seat. This is intentional. Our goal is not to pick winners; it’s about correctly estimating the probabilities. And for us to be successful in this regard, candidates with a 75/100 chance of winning must win 75 times out of 100 – and lose 25 times out of 100. Our final forecast puts 66 seats in a toss-up. “Skinny” or “Probable”. Based on how our model would have predicted similar elections in previous elections, we expect 14 of these districts to go to the party that is not favored to win. Additionally, we expect three losses in districts deemed “strong” for either party, meaning they have at least a 98 out of 100 chance of winning.

The senate

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

The Republicans’ strength in our forecast comes from their expected victories in Montana and Ohio, where moderate Democratic incumbents are trying to fend off stiff competition from Republicans. In Montana, the GOP has a 93/100 chance of defeating Sen. Jon Tester. In Ohio, Senator Sherrod Brown has a 41 in 100 chance of beating Republican businessman Bernie Moreno. And our forecast gives West Virginia Democratic candidate Glenn Elliott a 1 in 1,000 chance of retaining incumbent Sen. Joe Manchin’s seat.

If Democrats lose at least two of these seats, which we predict will happen about 95% of the time, they will need to gain another seat elsewhere to maintain their majority. Our predictions are that their best chances of doing so are in Florida or Texas, but they only have a 16/100 chance of winning each. It’s not nothing; it’s the chance to roll a standard six-sided die and roll a 1. But that’s still a pretty uphill climb for Democrats.

Our last word

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

In presidential and legislative elections, if polls deviate from a historically normal level, either party could win. In the Senate, polls are expected to be more wrong than they were in 2020 in at least one state. It’s possible, but given the other information we have about which seats are up for grabs, we think it’s unlikely that Democrats will hold the chamber.

Footnotes

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

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