ABC News projects that Trump will win the New Hampshire Republican primary. He currently leads Haley 53 percent to 46 percent with 15 percent of the expected vote reporting. And based on where ballots remain to be counted, I'd expect that margin to widen.

—Nathaniel Rakich, 538

According to preliminary exit polls, Trump is doing about 10 points better with men than women in New Hampshire. In earlier primary polls, he was running more evenly, or better, with women. With Ramaswamy and DeSantis out of the race (and their endorsement of Trump), Trump likely picked up more support from male voters.

—Meredith Conroy, 538 contributor

The first major news organization — the Associated Press — has called the New Hampshire Republican primary for Trump. Our colleagues at the ABC News decision desk, however, have not yet made a projection.

—Nathaniel Rakich, 538

There are a lot of arguments about whether the current nomination system that we have — influential early contests and the "invisible primary", where fundraising, polls and endorsements show which candidates have support — is effective. There's an argument that this system is effective at "winnowing" candidates who aren't able to unite the party behind them. But in the case of DeSantis dropping out on Sunday — unusual timing — it's not clear that this was especially effective winnowing. From a candidate perspective, maybe. DeSantis lost support as Trump gained it, and he didn't seem to especially strike people as an ascendant presidential figure.

DeSantis's departure from the race was good for consolidating the party around Trump at this stage, which is usually what parties want. But Trump is a complicated figure, and even as the GOP is increasingly his party, it's not totally straightforward. If your takeaway from the Iowa caucuses was that about 40 percent of caucusgoers preferred someone else, then it makes sense that a real contest between Trump and a competitor might have been good to have. Now the Haley campaign is trying to talk about a head-to-head contest. It's hard to know what a two-person race between Haley and Trump would have been like, and pretty difficult to imagine that Haley would be beating Trump now. But competition between Trump and an alternative might have been clearer if it had been a two-person race for longer.

—Julia Azari, 538 contributor

It's been only eight days since Iowa's first-in-the-nation caucuses last Monday, but a lot has happened since then. On the night of the caucuses, businessman Vivek Ramaswamy dropped out of the race and endorsed former President Donald Trump, and Florida Gov. Ron DeSantis followed suit on Sunday. With former Arkansas Gov. Asa Hutchinson also leaving the race last week, former U.N. Ambassador Nikki Haley is Trump's last major competitor standing.

And everyone has their eyes on New Hampshire as potentially the only state where Trump has a realistic chance of losing. Haley has invested heavily in New Hampshire and has been suggesting since early December that today's race would be the start of a competitive two-person primary between her and Trump. She's got her two-person race, but whether it will be remotely competitive remains to be seen. Trump has only continued to consolidate party support since his Iowa victory, and anything less than a convincing win for him would be surprising.

So when might we know? First polls will close tonight at 7 p.m. Eastern, and last polls will close at 8 p.m., which is the earliest time we could have a race projection. But as we did last week (when Trump's victory was projected only 30 minutes after caucuses had begun), we will of course be sticking around no matter what happens to see how each candidate does across the state and discuss what it could mean for the rest of 2024.

And that's not all! Granite State Democrats also have a primary today, and it's a weird one — New Hampshire is violating Democratic primary calendar rules by holding it so early. As a result, President Joe Biden isn't campaigning or even on the ballot, but his competitors, Rep. Dean Phillips and self-help author Marianne Williamson, are. While Biden isn't expected to face serious competition for the actual nomination, his margin of victory today as a write-in candidate could be one early sign of Democrats' grassroots enthusiasm for the incumbent.

Bookmark this page for updates and analysis throughout the night!

—Tia Yang, 538