That's true, Nathaniel. But maybe Haley is hoping that actively campaigning, and still having a campaign apparatus running, will give her an advantage over the other also-rans.

—Monica Potts, 538

Remember that the primary is ultimately all about the delegates candidates win to vote for them at the RNC in July. In the delegate math tonight, Trump is coming out way ahead. South Carolina awards delegates in two sets: 29 are awarded to the winner of the statewide popular vote (which are all going to Trump tonight) and the remaining 21 are split equally between the remaining 7 congressional districts. According to ABC's delegate projections Trump has already won 38 delegates tonight, with 12 left to assign in 4 more districts. But if Trump is heading for a 30-point margin statewide, it's unlikely Haley will win any of those that remain.

Our delegate benchmarks model had Haley needing all 50 tonight to be on track for the GOP nomination. It is her home state, after all.

—G. Elliott Morris, 538

Am I the only one who uses the term "bet your bippy"??

—Nathaniel Rakich, 538

Right, so why is Haley sticking around if Trump is the presumptive nominee? We've put together a few hypotheses — spite, in case something happens, sticking it to the man etc — but, as ever with politicians, we cannot discount the possibility that she's in it for her. I keep thinking of Beto O'Rourke's "born to run" comments in the 2020 primary. A lot of politicians think this way!

—G. Elliott Morris, 538

The Republican presidential primary started out in territory pretty friendly to Haley. That changes after today, making the South Carolina primary a sort of last chance for the former Palmetto State governor to prove she actually has a path to the 1,215 delegates necessary to secure the GOP nomination. It looks somewhere between unlikely and impossible that she'll be able to pull that off.

It's all about the numbers. According to the polls, Trump leads Haley by about 30 points among likely Republican primary voters. But his delegate lead is what really matters — and it's likely to be even larger. That's because the South Carolina Republican Party awards its delegates on a winner-takes-all basis. About half the delegates will go to the winner of the statewide vote (almost certainly Trump) and the remainder will go to the winner of each of the state's seven congressional districts. With a 30-point statewide victory, Trump would probably win every district resoundingly; in 2016, the largest difference between Trump's statewide margin (10 points) and his margin in the most anti-Trump county (which he lost by 5 points to Marco Rubio) was only 15 points.

This is all disastrous news for Haley, who needs all 50 delegates from the state to be on track to win the Republican nomination. The competition on and after Super Tuesday will be even tougher. According to the math powering 538's delegate benchmarks, Trump is leading Haley by around 57 points in California and 69 in Texas, the states with the largest delegate hauls on Super Tuesday. Those states also allocate delegates on a winner-takes-all basis, as long as a candidate wins at least 50 percent of the vote.

The primary, in other words, is functionally over. But because Trump has not yet clinched a majority of delegates, Haley's campaign technically has a chance of winning. It's just very, very low.

—G. Elliott Morris, 538