Of the three longstanding early state contests — Iowa, New Hampshire and South Carolina — the last of that group may actually be the best at indicating the eventual winner of the GOP nomination.

In the eight contested GOP primaries since 1980, when the state transitioned from a convention system to a primary, the winner of the election has gone on to win the nomination all but once. That aberration came in the topsy-turvy 2012 primary that saw three different Republicans win the first three early states; Southerner Newt Gingrich won South Carolina that year with 40 percent.

It makes sense that South Carolina has a stronger track record than Iowa (three of the eight) and New Hampshire (six of eight). (Nevada joined the early-voting lineup in 2008 and has picked the nominee in two of the three competitive GOP races since.) For starters, it has the advantage of sifting through a significantly winnowed field. It's not uncommon for a half-dozen or more candidates to seriously contest Iowa and New Hampshire, but by the time South Carolina rolls around, it's only the most viable contenders who remain.

But there's also something to be said for South Carolina being more representative of the GOP electorate as a whole. After all, it's the first solidly Republican state to vote — while Iowa and New Hampshire are historically swing states, South Carolina has voted Republican in every presidential election since 1980, when the primary began.

—Jacob Rubashkin, Inside Elections

Independent voters in South Carolina are much more likely to support Haley than those that identify as Republicans, according to an early February poll conducted by Winthrop University. Among likely GOP primary voters, those who identify as independent were split between Trump and Haley, with 43 percent saying they planned to vote for Trump and 42 percent saying they planned to vote for Haley. Among those who identify as Republicans, 72 percent said they planned to vote for Trump and 24 percent said they planned to vote for Haley.

—Mary Radcliffe, 538

Despite being Haley's home state, South Carolina is demographically much friendlier turf for Trump than Haley. Exit polls dating back to the 2012 Republican nomination race suggest that South Carolina's electorate will likely be more heavily Republican, more conservative and more religious than New Hampshire's.

In recent GOP primaries, at least 7 in 10 South Carolina voters identified as Republican and about a quarter called themselves independent. By contrast, only around half of New Hampshire's GOP primary voters called themselves Republicans, while more than 40 percent said they were independent. This should help Trump, who performs best among self-described Republicans. In New Hampshire last month, the exit poll found Trump attracted 74 percent of the vote among Republicans while Haley won 58 percent of independents. Recent South Carolina polls have found similar splits, with Trump surpassing 70 percent among Republicans and Haley narrowly ahead among independents.

Beyond party identification, Trump also stands to benefit from South Carolina's larger share of conservative-minded voters. More than 35 percent identified as "very conservative" in South Carolina's 2012 and 2016 GOP primaries, whereas New Hampshire's primary electorate didn't surpass 26 percent in that category in 2012, 2016 or 2024. And Trump does best among the most conservative voters in the polls: For instance, a Monmouth University/Washington Post poll of South Carolina in late January found Trump garnering 80 percent support among very conservative voters, compared with 59 percent among somewhat conservative voters and just 33 percent among moderate or liberal voters.

Trump's greater appeal among conservatives is connected to his increased support among white evangelical Christian voters. Voters who fall in that category tend to identify as more conservative than non-evangelicals, and they will likely make up a majority of South Carolina's GOP primary electorate. In 2012 and 2016, about two-thirds of GOP primary voters there identified as white born-again Christians, whereas less than a quarter said the same in New Hampshire. The late January Monmouth University/Washington Post poll found Trump attracting support from 69 percent of white evangelicals, compared with 46 percent of other voters.

—Geoffrey Skelley, 538

Haley may have come up through South Carolina politics, but her old colleagues are mostly supporting Trump. Both of the state's senators, its governor, its lieutenant governor, its attorney general, its secretary of state, its treasurer, its agriculture commissioner and five of its six Republican U.S. representatives have endorsed Trump. In fact, many of them announced their endorsement quite early in the campaign, when Trump visited South Carolina in January 2023 — a coordinated show of early strength in a rival's home state. By contrast, Rep. Ralph Norman is the only major South Carolina politician who is supporting Haley.

—Nathaniel Rakich, 538

It's not a huge surprise that Haley thinks she can win tonight despite the odds. Her first political success was in a 2004 South Carolina state House Republican primary, in which she unseated a powerful 30-year incumbent to win. She tells that story on the stump, and the message is clear: She's won as an underdog before.

As a legislator, Haley carved out a reputation in South Carolina as an outsider taking on state power. She sponsored a bill to force roll call votes on issues like raising legislator pay, losing support from her colleagues and a race for a committee chair position in the process. Later, as governor, she became known for luring businesses to the state, siding with business over labor, signing a 20-week abortion ban and blocking Medicaid expansion.

On social issues, though, she has tried to walk a middle path. Haley has talked about the racism her Indian American family faced in rural South Carolina, and supporters have said the "good ol' boys" network never quite accepted her in state politics. But she also frames her success as an example of how the South has made progress. She didn't tackle the issue of the Confederate battle flag flying over the State House until after a racist shooting in Charleston in 2015, in which nine churchgoers were killed in Emanuel AME Church. She has also sidestepped more recent controversies, like anti-transgender bathroom laws.

Of course, all of her history in the state hasn't seemed to help her against Trump. In polls, she's winning only about a third of potential voters. She may be used to playing the role of David, but not all Goliaths fall in defeat.

—Monica Potts, 538