I'm on the fence. As I pointed out, this would be panic-time for a sitting president running for reelection — evidence of a significant rift in the party. And it's not a mystery what that rift is — people in the Republican party who have reservations about Jan. 6, Trump's electability or his presidential temperament. At the same time, he has majority support in most polls, far outpacing any rivals.

—Julia Azari, 538 contributor

The first few primaries to me don’t seem to suggest the kind of strength that I would expect from a universally known, pretty well-liked (within his party) former president. So, is Trump doing well in this race, or is he just doing better than Haley? And does that mean anything for November?

—Mary Radcliffe, 538

The South has historically been a politically distinct region. This distinctive character — associated for a long time with strong, conservative Democratic affiliation — has been really important in explaining how the Democratic presidential nomination calendar has evolved. Super Tuesday was initially pushed to strengthen Southern influence and give an advantage to moderate candidates. South Carolina itself was moved to a more prominent spot in the primary calendar because many of its Democratic primary voters are African American — unlike in the traditional early states of New Hampshire and Iowa.

But what does this mean for Republicans? The South has been a Republican stronghold for most of the twentieth century, though Democratic presidential candidates have pulled off occasional victories. And South Carolina hasn't been a distinctly regional primary for Republicans (though Georgian Newt Gingrich won the GOP primary there in 2012). Nikki Haley doesn’t seem to be enjoying much home state (or region) advantage there. And Trump, who is from New York, is consistently popular in the South.

The larger point here is probably that, now that it’s generally in the Republican column, the South has been much less exemplary of unique regional politics, and instead has similar issue positions and priorities as other Republican strongholds.

—Julia Azari, 538 contributor

Only a third of the estimated vote is counted so far, but Trump is leading Haley only 59 percent to 40 percent. If that 19-point lead holds, it would be a pretty far cry from the 28-point lead that the polls foresaw, even though they “called” the correct winner. It’s a good reminder that polls of presidential primaries historically have a lot of error.

—Nathaniel Rakich, 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