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

There are a handful of particularly hot downballot contests in North Carolina worth paying attention to tonight. You can read about them in more detail in my preview from last week, but here's a quick recap to get you up to speed.

Neither the Democratic nor Republican primary for governor is competitive, but they're worth paying attention to because this race will be competitive come November. If Republican front-runner Lt. Gov. Mark Robinson — a deeply conservative Christian and controversial figure — wins the nomination and defeats Attorney General Josh Stein, who is leading the Democratic race, it would give Republicans a governing trifecta in the state for the first time in eight years.

Thanks to redistricting, North Carolina's 1st Congressional District is expected to be the state's only competitive congressional race this fall. Incumbent Democratic Rep. Don Davis will be squaring off against one of two Republicans: Jan. 6-attending, MAGA firebrand Sandy Smith and retired U.S. Army Colonel Laurie Buckhout, a wealthy businesswoman who has spent more than $1 million of her own money boosting her campaign.

Then there are four safely Republican open seats elsewhere in the state, where the GOP primary will effectively decide the next representative. In the 6th District, the six-candidate field includes Bo Hines, a former wide receiver for North Carolina State University who ran unsuccessfully in 2022. In the 8th District outside Charlotte, the two GOP front runners are state Rep. John Bradford, who has poured $1.3 million of his own money into his campaign, and Baptist minister Mark Harris, whose 2018 congressional win was thrown out due to allegations of ballot fraud.

In the 10th District, state Rep. Grey Mills is hoping to upset front-runner Pat Harrigan, a gun manufacturer who was the Republican nominee in the 14th District in 2022. And in the 13th District, there are no fewer than 14 candidates running — this one looks like a jump ball and may even go to a May 14 runoff if none of the candidates can clear 30 percent of the vote.

I'll have more on these races and more from the Tar Heel State soon! Polls close at 7:30 p.m. Eastern.

—Kaleigh Rogers, 538