Haley spent a good portion of her speech attacking Trump and Biden in equal measure. It definitely raised the specter of a third-party candidacy down the line, after she loses the GOP nomination, perhaps on the No Labels ticket. Haley has said she’s “not interested in talking” with the centrist group, but that doesn’t mean she can’t develop an interest later on.

And it’s not entirely unheard of for a losing GOP candidate to launch a more center-minded independent bid for president against an incumbent Democrat and the Republican who beat them in the primary. Illinois Rep. John Anderson did just that in 1980 against Jimmy Carter and Ronald Reagan. He ultimately won about 6.6 percent of the vote (5,719,850 popular votes, but no electoral votes).

—Jacob Rubashkin, Inside Elections

That electability case may not be resonating with actual primary voters, though. According to a January poll conducted by Monmouth University/The Washington Post, likely South Carolina GOP primary voters care more about issues than electability in choosing their nominee. Sixty-two percent said it was more important to nominate a candidate whose positions on the issues are closest to their own, while 33 percent said it was more important to nominate a candidate who seems most likely to beat Biden in November. There was little difference between Trump and Haley voters on this: 61 percent of Trump voters and 64 percent of Haley voters said that issue positions were more important, while 34 percent of Trump voters and 31 percent of Haley voters chose electability.

—Mary Radcliffe, 538

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

As of 9:20 p.m., 70 percent of the expected vote is reporting in South Carolina, and Trump is leading Haley by 20 points. It’s a decisive victory for the former president, as expected, though a somewhat smaller margin than his average lead in the polls heading into today (around 28 points).

Haley’s margin of defeat, though, looks even larger when it comes to delegates: Under South Carolina’s delegate allocation system, over half the state’s 50 delegates are awarded to the statewide winner, while the rest are awarded by congressional district. It looks like the maximum delegates Haley could walk away with in her home state tonight is three, if she holds onto her lead in the 1st District.

Despite this, Haley proclaimed in her speech that tonight’s result demonstrated her home state’s frustration with the country’s direction and reiterated her promise to stay in the race.

And on that note ... We hope to see you back here for our Super Tuesday live blog on March 5! We're gearing up for an eventful night tracking not only the presidential race in 15 states (and one territory) but a slew of down-ballot primaries in Senate, House and gubernatorial races as well.

—Tia Yang, 538