Haley addressed supporters at about 8:30 p.m. Eastern, and vowed to stay in the race: "I said earlier this week that no matter what happens in South Carolina I would continue to run for president, and I’m a woman of my word," she said. Haley said she was frustrated and worried about the future of the country and the world, and that she was running to save it. "America will come apart if we make the wrong choices," she said. Again, Haley presented her case as one of electability. She said that we couldn't live with four more years of Biden's failures or Trump's lack of focus, and that the voters in future primaries deserved a choice, not a "Soviet-style election" with one candidate. With about 40 percent of the vote (as of now), she noted that it was roughly the same amount she'd gotten in New Hampshire. "I’m an accountant. I know 40 percent is not 50 percent," she said. "But I also know 40 percent is not some tiny group." Those people were looking for an alternative, and she said she shared their frustration. The electability argument is one that Republican primary voters aren't buying.

—Monica Potts, 538

Political scientist Seth Masket has some interesting graphs comparing Trump's 2024 county-level vote share — based on what we know so far — to his 2016 performance in those counties, and it tracks pretty well. Meanwhile, Haley's performance is strongly related to Rubio's in 2016 at the county level - but not so much to Ted Cruz's.

—Julia Azari, 538 contributor

For the purposes of this analysis, I think we should view Trump as an incumbent when measuring his performance in the primary. Republican voters know exactly what Trump is like in the White House, and they can judge for themselves how he did on the issues they care about (he generally does well on this axis) and his character (things are more muddled here).

If we think of him as an incumbent, he is doing quite poorly. Remember how Pat Buchanan embarrassed H.W. Bush by getting 38 percent of the vote in New Hampshire in 1992 and is blamed for weakening him for the general? Haley has been doing better than Buchanan across the early states. There are plenty of Republican voters who don't think of Trump as ideal. We've probably all heard their arguments. Something along the line of, "his character isn't ideal, but he fights for me."

Now, what does this all mean for the contest against Biden in the fall? Not much. The vast majority of those people will vote for Trump in the fall. And if we are sticking with the 1992 comparison, Bill Clinton was a popular candidate (net +11 favorability in September of '92). Joe Biden is not. His favorability rating is currently at net -15 points. So, Trump is doing poorly, but so is Biden. When it's a race to the bottom all around, doing poorly in a GOP primary doesn't tell us all that much.

—Galen Druke, 538

I see your point, Mary — Trump has gotten “only” around 50-60 percent in the first three contested states — but I think in the grand scheme of things, that’s still a strong performance. Iowa winners much more often finish in the 20s or 30s, and New Hampshire is just weird because of its demographics and high proportion of independent voters. And at the end of the day, he’s the first non-incumbent Republican to win all three of Iowa, New Hampshire and South Carolina, and there’s a good chance he’s going to win all 56 contests.

—Nathaniel Rakich, 538

If you are looking for something to listen to while we wait for polls to close and results to come in, allow me to suggest our latest episode of the 538 Politics podcast. We talk about what to expect tonight, including how South Carolina's primary electorate is different from that of other early states and how the results might shape what Haley does next. We also had a debate about a recent poll on presidential greatness and looked at polling that suggests the wars in Ukraine and Gaza have created some significant divides within the two parties.

—Galen Druke, 538