Super Tuesday primaries 2024: Trump and Biden dominate, Haley drops out

538 tracked how Trump and Haley did, plus key U.S. House and Senate races.

March 5 was Super Tuesday — the biggest election day of the year until the one in November! With former President Donald Trump projected to win 14 of the day's 15 GOP presidential nominating contests, former U.N. Ambassador Nikki Haley announced Wednesday morning that she is suspending her campaign.

It was also the first downballot primary day of 2024, with important contests for Senate, House and governor in states like Alabama, California, North Carolina and Texas.

538 reporters, analysts and contributors broke down the election results as they came in with live updates, analysis and commentary. Read our full live blog below.


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Downballot, Trump’s endorsees are winning in Texas

As Nathaniel and I discussed earlier, dynamics in the Texas state legislative elections have been particularly contentious this year, with the governor and Trump endorsing at least eight challengers to Republican incumbents in the state House. As of now, seven of those challengers are currently leading their primaries, though a few look headed to a runoff. One challenger, Barry Wernick in the 108th, is trailing by just 2 points.

—Mary Radcliffe, 538


It’s ovah in Minnesota

ABC News projects that Biden will win the Minnesota Democratic primary, and Trump will win the Republican primary. Biden’s win is expected, but also salt in the wound for his highest-profile competitor, Minnesota Rep. Dean Phillips, who gave up a safe seat in Congress and the potential for a strong statewide run in a few years to launch his no-shot challenge against Biden.

Jacob Rubashkin, Inside Elections


Trump projected to win Massachusetts

ABC News projects that Trump will win the Massachusetts primary, his 10th win of the evening. With 15 percent of the expected vote reporting, Trump is leading Haley in the Bay State 59 percent to 37 percent. Yet again, this is another state where Haley was hoping to do well: Massachusetts has a lot of college graduates, and it allows independents and Democrats to vote in the Republican primary. But with Trump’s win, the Haley campaign turns its lonely eyes to Vermont.

—Nathaniel Rakich, 538


Trump opens up lead in Vermont

With 56 percent of the expected vote now reporting, Trump has opened up a bit of a lead against Haley in Vermont. He has half the vote, and Haley is just behind him with 47 percent. Still, that's closer than the two polls, had us expecting. There's still room for Haley to pull out a win, which she would need: all of the state's 17 primary delegates go to the winner. That is, unless they both end up with under 50 percent of the vote, in which case they split the delegates proportionally.

—Monica Potts, 538


More thoughts on primary polls

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