With 24 percent of the expected vote reporting, Trump is leading in Texas by 53 percentage points. Despite Trump's 65-point lead in the polls, likely GOP primary voters in Texas thought the race would be close in pre-election polling. In a February survey from the University of Texas at Tyler, just 17 percent of likely GOP primary voters in the state thought Trump would win by a large margin, while 21 percent thought that Trump would win in a close election. Another 6 percent said they thought Trump would win, but weren't sure of what the margin would be. Most of the rest, 46 percent, said they weren't sure who would win, and just 3 percent thought Haley would win.

—Mary Radcliffe, 538

ABC News projects that Trump will win the Tennessee Republican primary, his fourth win of the evening (and the night is young). Demographically, Tennessee was one of the best states for Trump, and it hasn't let him down tonight: He's currently leading 81 percent to 16 percent.

—Nathaniel Rakich, 538

Trump looks well on his way to a clear victory in Virginia. With 46 percent of the expected vote reporting, he leads Haley 66 percent to 32 percent.

If we look at a map of Virginia's counties and independent cities, we can see how Haley failed to break through. To be competitive, Haley needed to perform well in the state's three major metro areas: Northern Virginia outside of the nation's capital, around the state capital of Richmond and in Hampton Roads, the southeast corner of the state. Yet she's mostly striking out so far.

So far, she only leads in the inner D.C. suburbs (including the state's largest county, Fairfax) and in the city of Richmond proper. She will probably gain as Fairfax reports more, but critically, Trump leads in Loudoun and Prince William counties, the other two big population centers in Northern Virginia. Trump is also ahead around Richmond and leads everywhere in Hampton Roads. And his strength in the rural areas is very strong, much as was the case in the 2016 GOP primary here. Haley holds leads in the city of Roanoke and in the Albemarle County-Charlottesville City area, but it's far from enough to make the race interesting.

—Geoffrey Skelley, 538

ABC News also projects that Biden will win in Vermont and Oklahoma, two of the states I'm watching tonight. Biden is a favorite to win across the country, but there is still a Democratic primary tonight.

—Monica Potts, 538

Super Tuesday has over 40 years of history that are deeply entwined with a bunch of issues in the presidential nomination process. The term "Super Tuesday" was first used in 1980 but was promoted by Democrats in 1988 as a deliberate effort to give an advantage to more moderate candidates. This was a direct reaction to the idea that the party's 1984 nominee, Walter Mondale, had lost to Ronald Reagan because he was too liberal. This strategy didn't really work out, though, and Democrats ended up nominating another northern liberal, Michael Dukakis.

In other words, this early attempt at a Super Tuesday brought some of the disadvantages of a regional primary, reducing the amount of attention on individual states and pressuring states to move their primaries earlier without really strengthening the influence of the region. Another drawback was that, by trying to enhance Southern influence by holding contests early, Super Tuesday also contributed to the "front-loading" problem", or the issue of having too many delegates selected at the beginning of the primary calendar.

Over time, Super Tuesday has taken on other significance as an important turning point in the race. As party politics scholar Caitlin Jewitt noted, in 2016, everyone thought that Sen. Ted Cruz needed to do well on Super Tuesday, which was heavily concentrated in Southern states where he needed to rack up wins — and when that didn't happen, it was a significant blow to his candidacy. For Biden in 2020, Super Tuesday marked the point when the party consolidated behind him. And in 2008, Super Tuesday made it clear that the Democratic nomination was a real race between Hillary Clinton and Barack Obama, as neither one scored a decisive victory.

It's hard to know exactly how this will play out in 2024. Republicans don't have the same ideological history with the big primary day as Democrats do. But the potential for a turning point in the race is there: Because so many delegates are at stake today, unless Haley wins a significant share of them, it may not make sense for her to stay in the race after tonight.

—Julia Azari, 538 contributor