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

After Trump's New Hampshire primary victory, political commentators noted that he made history as a modern-era non-incumbent winning both major early contests – Iowa and New Hampshire. But while it's obviously true that he's not the sitting president, is it really fair to call Trump a non-incumbent when it comes to the dynamics of the primary race?

In some senses, Trump has campaigned like an incumbent. He refused to participate in any of the primary debates. He uses some of the visual trappings of the presidency, like a modified version of the presidential seal, in public appearances. And he acts like the leader of his party. After his allies played a role in pressuring Republican National Committee Chair Ronna McDaniel to step down, Trump is reportedly looking into replacing her with someone more loyal to him — possibly even his daughter-in-law, Lara Trump. As Trump's preferences and personal brand increasingly dominate the party, and he continues to barrel toward winning the nomination, his influence over the GOP seems very much like what an incumbent president might expect to wield.

But thinking of him this way raises very different expectations for the nomination contest. As a candidate in an open race, Trump has done very well against a field of highly qualified opponents. But unlike most incumbents, he's attracted a lot of challengers. Almost half of Iowa caucusgoers chose someone else, and Trump won by 11 percentage points in New Hampshire. These results would be concerning for an incumbent president. (Imagine the narratives we'd see if Biden was facing a field of strong primary competitors who siphoned off more than a third of the vote in early states.) Based on those numbers alone, it may look like Trump's challengers managed to do just well enough to suggest that if anti-Trump forces in the GOP could just coordinate, they might have been able to compete with him. But of course, tonight could put a fine point on the reality that that opportunity has passed and, incumbent or not, Trump is still in the driver's seat of the GOP.

—Julia Azari, 538 contributor

538's research team, Mary Radcliffe and Cooper Burton, has been collecting data on how many campaign events each presidential candidate has held in each state, and one consistent pattern has been that Trump holds a lot fewer events than more retail-politics-focused candidates like Haley (and, before they dropped out, Ramaswamy, DeSantis, etc.).

That has certainly been the case in South Carolina. From their respective campaign launches through Friday, Haley had held 52 public, in-person campaign events all over the Palmetto State, while Trump had held only eight — mostly in major urban areas like Columbia and metro Charleston.

Of course, it may not matter. Political science research on the impact of campaign events is mixed, and the polls indicate that Trump is cruising to an easy win tonight despite not campaigning very hard here.

—Nathaniel Rakich and Amina Brown, 538