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

I have become a little obsessed tonight about what we should be expecting Trump to hit in this primary a priori. That is, given Trump is assumed to be the eventual party nominee and almost universally liked in the GOP, should he be winning more than 60 percent in South Carolina?

I already gave my case for answering "no" to that question: Strictly speaking Trump is dominating the delegate count and running ahead of his 2016 vote share in most counties with complete counts this primary cycle. And if you consider that Haley gets a home-state advantage in South Carolina tonight, Trump's adjusted vote share is close to 65 or 70 percent; our delegate benchmarks think Trump should have won 68 percent of the vote based on the demographics of the state alone. That's not the highest number, but it's not the lowest right? Would 65 percent be "good" for Trump? 75 percent? 80?

One counterargument to this centers around how the media has covered historical performances by incumbent presidential candidates. Journalist Jill Lawrence points out that in 1992, Patrick Buchanan challenged incumbent President George H.W. Bush for the GOP nomination and won 40 percent in the New Hampshire primary, holding Bush to 58 percent of the vote. That's an almost identical split to the results from tonight. The New York Times journalist Robin Toner wrote up the results with the headline "BUSH JARRED IN FIRST PRIMARY" and said the result "amounted to a roar of anger" from Republican primary voters.

If Trump was a true incumbent, I imagine the news media would use a similar headline to describe tonight's results in South Carolina. Perhaps our expectations for him are too low, or we're too focused on the broader state of play? Haley said in her concession speech tonight that she will stay in the race indefinitely, so I guess we'll get more data on Super Tuesday — only 10 days from now. The primary lives on!

—G. Elliott Morris, 538