I actually don't think polls are overestimating Trump by much, more that they're underestimating Haley. And I think it really comes down to undecided voters. Trump is a known quantity for pretty much everyone in America. So anyone who isn't sure if they're going to vote for him isn't unaware of his issues, but probably has some doubts about him. So my theory is that undecided voters skew, if not anti-Trump, at least Trump-skeptical and are disproportionately choosing Haley. You can see an inkling of that in the preliminary exit poll data: In Virginia, for example, voters that decided their vote choice earlier than this year went overwhelmingly for Trump (78 to 21 percent), but voters that made their decision later chose Haley (54 to 42 percent).

—Mary Radcliffe, 538

Polling nowadays is incredibly hard. Seeing response rates of under 2 percent is all too common. So even very slight differences in how fired up people are to take polls can translate into meaningful differences between polls and results. Primary polling is especially hard because you can't use partisan identification to benchmark how reasonable the sample looks. That all said, in New Hampshire and in South Carolina, I wonder if Haley may have benefited from the lack of a competitive Democratic primary, and the fact that some who might have otherwise voted in a Democratic primary were able to vote for Haley.

—Dan Hopkins, 538 contributor

What's everyone's favorite theory about why polls have seemed to consistently overestimate Trump support? (I know this was discussed some on the podcast.)

—Julia Azari, 538 contributor

Tonight I'll also be watching my home state of Arkansas, where polls just closed. There hasn't been recent polling on the GOP presidential primary there, but Trump remains popular in the conservative state, which he won 62 percent of the state in the 2020 general election. His former press secretary is the governor, Gov. Sarah Huckabee Sanders, and she endorsed him in the fall.

There's not much suspense downballot either. Rep. Steve Womack, who represents the northwest corner of the state—home to the University of Arkansas, Walmart, and other big businesses and booming towns—is fending off an unlikely challenger from his right and is the only Republican incumbent to face a challenger. That challenger, State Sen. Clint Penzo is against vaccines, the war in Ukraine, government spending and has criticized Womack's votes during the House speaker fight last fall. But Womack has represented the district for 13 years and all the advantages of incumbency.

On the Democratic side, all four candidates for the House are running uncontested.

Perhaps of a bit more interest — earlier, I wrote about the state Supreme Court races and how the outcomes there could result in a game of musical chairs leading the very conservative Sanders to make one or two appointments to the court.

—Monica Potts, 538

It's just past 2 a.m., and we've got major results in from most of Super Tuesday's wide-ranging slate of primary contests. So far, Trump has won at least 12 of the 15 states holding GOP presidential nominating contests, while Haley has won Vermont — though whether she hits a 50 percent (plus one vote) threshold of victory there will determine the exact number of delegates she takes home.

Either way, with an estimated 943 total delegates to Haley's 86 so far, per ABC News projections, Trump's well on his way to securing the magic delegate majority number of 1,215 — though it will take at least another week. He's so far secured 667 delegates tonight and is likely to hit the 769 mark that Elliott noted earlier would set him up to mathematically clinch the nomination on March 12. Of course, we're all watching to see if Haley drops out sooner.

In other highlights:

- As expected, Republican Lt. Gov. Mark Robinson and Democratic state Attorney General Josh Stein secured their parties' respective nominations, and will go head to head in what's expected to be a close general election contest for governor.

- Rep. Colin Allred locked up the Democratic nomination in Texas's Senate race, and will face off against Sen. Ted Cruz in the general.

- Democratic Rep. Adam Schiff secured not only the top spot in a top-two primary, but also a likely glide path to the nomination, as the second spot on November's ballot went to Republican Steve Garvey instead of a second Democrat.

We're still tracking a dozen-odd downballot races that have yet to be projected, and awaiting presidential primary results in Utah and Alaska, so we'll see you back here tomorrow ... er, later today, with more results and analysis!

—Tia Yang, 538