The 2024 presidential race is shaping up to be one of the closest in our nation’s history. And yet, somehow, it keeps getting tighter and tighter. Several weeks ago, ABC News’s FiveThirtyEight election forecast gave Vice President Kamala Harris only a 58-100 chance of beating former President Donald Trump, but that number has undergone a rather significant change with only 18 days to go before election day. Trump now has a 52-100 chance of winning the election in the forecast, which takes a polling average derived from high-quality polls.

🚨BREAKING

Trump favored to win by Five Thirty Eight for first time since August pic.twitter.com/ucQVagbt4G

— Luc J. Gagnon 🇺🇸 (@LakePoliticsYT) October 18, 2024

FiveThirtyEight explained the recent movement in the forecast in a lengthy report discussing polling trends:

The reason our forecast is close is that the polls are close — well within the range that even a small polling error could be decisive. According to our polling averages, the margin between Trump and Harris is 2 percentage points or less in all seven major swing states (Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin). And in our average of national polls, Harris leads Trump by only 2.0 points. That is tighter than the margin between Trump and President Joe Biden on every day of the 2020 campaign, and tighter than the margin between Trump and former Secretary of State Hillary Clinton on every day between Oct. 1 and Election Day 2016. (Because of the Electoral College’s bias toward Republicans, our model currently estimates that Harris likely needs to win the national popular vote by 2.0 points in order to be favored to win a majority of electoral votes.)

For the most part, recent high-quality polls have only affirmed the closeness of the race. An ABC News/Ipsos poll fielded Oct. 4-8 found Harris up by 2 points nationally. An Oct. 1-10 survey from Marquette University Law School, one of the most accurate and transparent pollsters in America, found her up by 3 points. The list goes on: YouGov/CBS News recently gave Harris a 3-point lead; Marist College gave her a 5-point lead; Fairleigh Dickinson University a 3-point lead. Fewer pollsters have given Trump a lead nationally, but there have been a few: Beacon Research/Shaw & Co. Research/Fox News found Trump up 2 points; Hart Research Associates/Public Opinion Strategies/NBC News put him up by 1.

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National polls have been both tight and incredibly stable. Not much has changed in the last two months, as Harris continues to hold a 2.0% margin, the same polling edge she held on August 18. However, where there is movement, “most of it” is “against Harris.” 538’s report continues:

State polls, however, have shown comparatively more movement — and most of it against Harris. Compared to her numbers at the start of the month, Harris has lost ground in all of the seven key swing states. This is why her chance of winning in our forecast has decreased. In American presidential elections, you don’t get points for winning the national popular vote. One question that we sometimes get is whether polling averages like 538’s are biased toward Trump because of the influx of polls conducted by Republican-aligned firms. Over the past two weeks, 23 of the 121 polls released in the seven main swing states were from a Republican pollster or sponsor.** Only four were from Democratic organizations, and the remaining 93 were nonpartisan.

With a few weeks left in the race, anything can happen. During the last few weeks of the election in both 2016 and 2020, polls fluctuated by 4 points and 2 points, in former president Donald Trump’s favor.