Turning back to the high-stakes GOP primary in Alabama's 1st District, Moore leads Carl 55 percent to 45 percent, with 87 percent of the expected vote reporting. This undoubtedly makes Moore a favorite to win, but it's not over just yet. That's because 90 percent of the expected remaining votes are in Mobile County, Carl's home base. So far, Carl has carried Mobile 72 percent to 28 percent. That's been extremely helpful to him, but he'll need to win the remaining votes by an even larger margin if he wants to catch Moore: Based on the remaining votes, that same vote share would only get Carl to 48 percent (to Moore's 52 percent).

—Geoffrey Skelley, 538

For those just joining us, here’s the scorecard in the presidential race tonight. Trump has won 12 contests thus far, while Haley has won only one (Vermont). We are still waiting for a winner to be projected in Utah and Alaska.

—Nathaniel Rakich, 538

Now that the California Senate race has been projected, and more or less matches what we expected from pre-election polling, Schiff and Garvey will move on to the general election. Voters priorities in the state reflect its Democratic bent, giving us more hints that Schiff is well-positioned for a big lead in the general.

In polling before the primary, voters said abortion was the most important factor for their senate vote. In a late February University of California Berkeley/Los Angeles Times survey, 55 percent of likely California primary voters say that being "a strong voice in defending abortion rights" is very important to their Senate vote, more than any other candidate quality tested. For voters that say they plan to vote for Schiff, Porter or Lee (the top three Democrats in the race), 84 percent say defending abortion is very important, compared to just 15 percent among those who say they plan to vote for Garvey, the leading Republican.

Other top candidate qualities in the survey include being "a strong opponent of Donald Trump" (51 percent say this is very important) and supporting tougher immigration laws (46 percent). Among the top four candidates, Lee supporters were the only group among which a majority (63 percent) said supporting an immediate cease-fire in Gaza is very important, compared to 42 percent of Porter supporters, 33 percent of Schiff supporters and 13 percent of Garvey supporters.

—Mary Radcliffe, 538

In a few races, the Democratic Congressional Campaign Committee has endorsed a candidate ahead of the primary — a relatively rare step for the group. Most of those candidates are doing pretty well tonight. In Texas, Michelle Vallejo easily clinched the nomination for the 15th District, which is the only really competitive House seat in the state. In California, most of the DCCC's candidates don't actually have primary challengers, but one, Rudy Salas, is in a tough fight for a spot in the general election. Democrats are anxiously hoping to avoid a lockout in the 22nd District, where Salas is looking for a rematch against Republican David Valadao.

—Jacob Rubashkin, Inside Elections

Four years ago, Super Tuesday was one of the last big news events before the declaration of the COVID-19 pandemic. Just days later, the U.S. and much of the world would go into lockdown in an effort to stem the virus's spread.

As Julia noted, in 2020, Super Tuesday marked the point when the Democratic Party consolidated behind Biden. But I think that, partly because of the pandemic, even close observers of American politics don't appreciate just how unlikely Biden's Super Tuesday comeback was.

This year in Iowa, Ron DeSantis's second-place finish with 21 percent of the vote was enough to effectively end his campaign. But in 2020, Joe Biden came in fourth in the Iowa Democratic caucuses.

Similarly, pundits have viewed Trump as the prohibitive favorite in the 2024 race since at least his New Hampshire victory, when he topped Haley 54 percent to 43 percent. In 2020, however, Biden's New Hampshire performance was far weaker than Haley's this year — he finished fifth in the state, winning just 8 percent of Democratic primary voters.

But in a very short period four years ago, Biden resurrected his campaign. He convincingly won South Carolina on Feb. 29 thanks to his strength with Black voters, who had been few and far between in Iowa and New Hampshire.

Then, both Amy Klobuchar and Pete Buttigieg endorsed Biden in the run-up to Super Tuesday, consolidating the more moderate side of the Democratic Party against Bernie Sanders. That, in turn, positioned Biden for a decisive Super Tuesday win that made him the front-runner in short order. While Sanders won California, Biden won 10 states, including Massachusetts, North Carolina and Texas.

What explains the dramatic change in Biden's fortunes over a few short days leading up to Super Tuesday in 2020? In his book "Learning from Loss," political scientist Seth Masket emphasizes the Democrats' overwhelming aim to defeat Trump, and to find a candidate who gave them the best chance of doing so. At the time, there was evidence that Biden ran better against Trump than other Democrats. Many Democrats were willing to follow the cues of party leaders about their most competitive candidate, and in doing so, they vaulted Biden to the nomination.

In this year's GOP primary, there's some evidence that Haley may be a stronger general election nominee than Trump. But in a late-November survey I conducted via YouGov, GOP voters overwhelmingly saw Trump, not Haley, as their strongest candidate, and there's no evidence that's changed. So on the Republican side, the grounds for a similarly sudden Super Tuesday switch just aren't there.

—Dan Hopkins, 538 contributor