In polling conducted since the New Hampshire primary, Trump is viewed favorably by an average of 73 percent of likely South Carolina Republican primary voters, while Haley's average favorability is 51 percent. These numbers are slightly better for the former South Carolina governor than national polling, which, according to 538's tracking, shows 43 percent of Republicans have a favorable opinion of Haley and 81 percent have a favorable opinion of Trump.

—Mary Radcliffe, 538

Spoiler: Whoever wins the Republican primary is probably going to win the state in the general election. Trump beat Biden there by 12 points in 2020, and South Carolina has voted almost exclusively for Republicans in presidential elections since Civil Rights legislation under President Lyndon Johnson flipped most of the South from blue to red. The one exception? The state voted for the Democratic governor of neighboring Georgia, Jimmy Carter, in 1976.

The state reliably votes conservative in other elections too. Its governor, both senators, and six of its seven representatives are Republicans. And many Republican voters there seem fiercely loyal to the former president. Former Rep. Tom Rice, one of ten Republicans who voted to impeach Trump in the House after Jan. 6, was ousted in his midterm primary in 2022.

That said, South Carolina may be changing. Last year it was the fastest-growing state in the country by population growth, driven by the state's growing economy and its relatively affordable cost-of-living. In fact, nearly [10 percent of the potential voting population])) moved to the state since Haley left the governorship in 2017.

While many of those newcomers may have come from the more expensive coasts along the Northeast corridor and California, they don't necessarily seem to be changing the state's GOP electorate, as Haley has struggled to overcome Trump's popularity and name recognition among Republican-leaning new residents. Newcomers or no, Haley's challenges winning over voters in her home state seem not so different from her efforts in the rest of the country.

—Monica Potts, 538

Mathematically, Trump can't clinch a delegate majority until the March 12 primaries and caucuses, but he could sew up the nomination earlier if Haley were to suspend her campaign before then. With Haley staring down a potentially sizable defeat in South Carolina, it's possible she could drop out shortly after today's contest. If she did, the 2024 Republican race would rank as the shortest competitive presidential primary since the modern nomination process took shape in the 1970s.

As of today's contest, only four states (plus the U.S. Virgin Islands) have cast ballots. The race ending today — or even after Michigan's primary next week — would beat out the current records for the earliest end date (March 3 in the 2004 Democratic contest) and the lowest number of voting states (19 in the 2000 Democratic race).

An unusually drawn out early voting period likely played a role in winnowing the number of contests candidates could remain viable for: The period from Iowa through South Carolina lasted 41 days, the longest duration from first to last early states since Nevada became an early-voting state in 2008. As a result, Trump could become the presumptive nominee earlier than ever by calendar date and despite barely any states having voted.

Despite that drawn-out early period, the 2024 GOP primary could also be the shortest by the number of days in its competitive period, although that's up for debate. Based on political scientist Caitlin Jewitt's formulation, the 1992 Democratic contest is the shortest ever, having lasted 39 days until former Massachusetts Sen. Paul Tsongas suspended his campaign and left Arkansas Gov. Bill Clinton as the only viable Democratic contender. But the race technically kept going because a candidate with no chance of winning — former California Gov. Jerry Brown — stayed in to push a reform message on issues like campaign finance. If Haley drops out tonight, the 2024 Republican race would last 41 days — a tad longer than the 39-day mark, but also arguably shorter because Brown remained a thorn in Clinton's side beyond it in 1992.

—Geoffrey Skelley, 538

Majorities of likely South Carolina GOP primary voters said they thought both Trump and Haley are part of the Republican establishment, according to an early February poll from YouGov/CBS News. Seventy-five percent of likely primary voters in the state said Haley is part of the establishment, and 58 percent said the same about Trump. That's not necessarily negative for voters though; in the same survey, 42 percent of likely primary voters said that they thought of the term "Republican establishment" as positive, 33 percent said it was negative, and 25 percent said it was neither positive nor negative.

—Mary Radcliffe, 538

The polls are now closed in South Carolina, and based on an analysis of the exit polls, ABC News is projecting that Trump has won the state’s Republican primary. We’ll be sticking around for a while yet, though, to see what the exact margin is, how many delegates Trump will win and whether Haley will drop out following this decisive defeat.

—Nathaniel Rakich, 538