Haley took the stage in a bright red dress and in front of a row of American flags just after 10 a.m. from South Carolina, and announced she was suspending her presidential campaign. She began with a retrospective of the start of her campaign, and reiterated her conservative principles, including a low national debt, a small federal government and the need to promote democracy worldwide by standing by America's allies. With that, the final Trump challenger is out of the race, and Trump is the presumptive nominee, a fact Haley acknowledged.

Like most major candidates who ran for the Republican nomination, other than Trump, Haley had previously signed the RNC's pledge to support the eventual nominee, but she's distanced herself from that pledge a bit recently. Haley didn't endorse Trump this morning, but she did congratulate him, while slightly criticizing the way that he's run his campaign. "We must turn away from the darkness of hatred and division," she said. She went on to say that Trump needed to bring people into his cause, saying, "It is now up to Donald Trump to earn the vote of those in our party and beyond it." Haley has noted in previous speeches that she's captured a sizable portion of the vote in some states, even winning Washington, D.C., and Vermont, signaling that some Republican voters are dissatisfied with the former president as a choice for the future.

In the end, as Meredith noted, she made a somewhat rare reference to the historic nature of her campaign. She's the first Republican woman win any state's nominating contest, and she noted that her mother, a first-generation immigrant, had gotten to vote for her for president in South Carolina. She directed her final lines, quoting from the Book of Joshua, to women and girls who had watched her campaign.

—Monica Potts, 538

Back in late January, we wondered if the 2024 Republican presidential primary might be the shortest in modern history. But because Haley continued to contest the race until Super Tuesday, the competitive period of this year's GOP contest ended up falling short of setting any records. Still, it was undoubtedly on the quick side, historically.

The 2024 Republican race lasted 52 days from Iowa through today, during which time all states and the District of Columbia held 25 contests. The March 6 effective end date puts it just behind the record earliest end of a nomination season (March 3 in the 2004 Democratic contest) and the number of state-level elections (19 in the 2000 Democratic race). Nonetheless, going back to the 1976 election cycle, this year's Republican campaign was much shorter than the median number of competitive days (85 days), state-level contests (39) and end date (April 9).

To be clear, measuring the effective end date of a nomination race's competitive period is not always cut and dry, although it was this time around. We based our approach on political scientist Caitlin Jewitt's work on presidential primary competition, which classified a candidate as their party's presumptive nominee either when all viable opponents have dropped out or when they clinch a delegate majority from the results of primaries and caucuses. In Trump's case, Haley was his last viable opponent.

—Geoffrey Skelley, 538

This morning, as Haley was dropping out, Trump sent a message over his social media platform Truth Social reacting to the results:

"Nikki Haley got TROUNCED last night, in record setting fashion, despite the fact that Democrats, for reasons unknown, are allowed to vote in Vermont, and various other Republican Primaries. Much of her money came from Radical Left Democrats, as did many of her voters, almost 50%, according to the polls. At this point, I hope she stays in the "race" and fights it out until the end! I'd like to thank my family, friends, and the Great Republican Party for helping me to produce, by far, the most successful Super Tuesday in HISTORY, and would further like to invite all of the Haley supporters to join the greatest movement in the history of our Nation. BIDEN IS THE ENEMY, HE IS DESTROYING OUR COUNTRY. MAKE AMERICA GREAT AGAIN!!!"

—Nathaniel Rakich, 538

In her short remarks, Haley quoted Margaret Thatcher: "Never just follow the crowd. Always make up your own mind." She used this quote to encourage the likely nominee, Trump, to appeal to the primary voters who he hasn't won over. She also thanked the girls and women who have supported her campaign, as another (subtle?) reminder of her historic run.

—Meredith Conroy, 538 contributor

It has become somewhat of a theme of our live blogs this primary calendar to note that Trump's challengers are beating their polls. This first looked to be the case in New Hampshire, where polls significantly underestimate support among Republican likely voters for Haley. But the pattern is more robust than one state: In fact Haley has been beating her polls by an average of five points (in vote share) once you account for undecided voters in these surveys. The consistency of this pattern is striking enough to warrant a post on the matter.

As Mary said earlier, polling primaries is hard! That is betrayed by the fact that POTUS primary polls are by far the least accurate type of poll in 538's pollster rating database going back to 1999. But error is different than bias, and when most of the polls are off in the same direction, something has gone awry.

That "something" is likely the difficulty in obtaining opinions of moderate Republicans from samples of "likely Republican primary voters." Remember that fewer than one percent of people called for a poll actually complete the interview. That means the ones that do are statistical "weirdos" (excuse the technical language). Pollsters adjust for this by weighting their samples to known population benchmarks — like the percent of all adults who are white, over 65, have a college education etc. But in primaries, such benchmarks do not actually exist; pollsters are just making educated guesses about them.

My theory is that most of these primary polls pulling samples of voters from voter registration lists are missing moderate crossover partisans and first-time voters. Additionally, we know that people who are highly motivated to participate in polls (the "weirdos") also happen to be the most politically and ideologically extreme Americans. That's a recipe for polling bias in primaries, where weighting to party, past vote and polarized demographic benchmarks does not control for the partisan consequences of overrepresenting politically engaged Americans.

Now, none of this is to say that polling is "broken." It's just hard to precisely sample a population that doesn't really exist. The polls for the 2024 primary still have below-average error, historically speaking, so we shouldn't go throwing out the baby with the bathwater. But this could nevertheless be a sign of pollsters having a hard time reaching moderate "normie" voters. And if that persists, it could have consequences for general election polls too.

—G. Elliott Morris, 538