As Meredith and Monica noted, Haley really emphasized electability in her speech. The difficulty with that argument is that poll after poll shows Republicans think Trump is electable in the general. For example, this YouGov/The Economist poll from early January shows 82 percent of Republicans saying Trump would definitely or probably win the general election, but only 37 percent say the same about Haley.

—Mary Radcliffe, 538

Haley promised to stay in the primary race at a speech tonight just after 8 p.m., when most news organizations had projected the race for Trump. She again made her pitch as one of electability, and slightly attacked the front-runner, Trump, to cheers from the crowd. "The worst kept secret in politics is how badly the Democrats want to run against Donald Trump," she said, saying Biden could defeat him but that she could win. With Trump, the story is court cases, chaos, and senior moments, she said. "I've long called for mental competency tests for politicians over the age of 75," she said. "Trump claims he'd do better than me in one of those tests. If he thinks that, then he should have no problem standing on a debate stage with me." It's unlikely Trump would debate her, but the crowd in New Hampshire ate it up, calling Trump a loser and geriatric. "The first party to retire its 80-year-old candidate will win this election," she said. We'll see in her home state of South Carolina, in about a month.

—Monica Potts, 538

Dan, I'm not sure why Trump would risk getting on stage with her, especially when he can just snipe from Truth Social or in whatever town halls get scheduled between now and then. Avoiding the debates has worked wonderfully for Trump so far, and now that he's won New Hampshire, I don't see him adjusting that strategy. I think it would take an actual loss for him to feel pressured to show up. In fact, I don't think we'll see Trump on a debate stage at all this cycle, in the primary or general election.

—Jacob Rubashkin, Inside Elections

In her post-primary speech, Haley tries to goad Trump into a debate. The question is: can Trump resist calls to debate in the long interregnum between now and the South Carolina primary? He has resisted them so far.

—Dan Hopkins, 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