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

As I mentioned earlier, 2018 was a watershed year for political ambition among Democratic women. Not only did Democratic women run in record numbers in 2018, they also outperformed Democratic men in their primaries. And in November of that cycle, female candidates were responsible for more than 60 percent of the congressional seats that flipped from red to blue. That year was a nail in the "women aren't electable" coffin.

There are a few Democratic women running tonight who are vying to do just that once again.

In southern California's 40th District, which spans parts of Orange, Riverside and San Bernardino counties, engineer Allyson Muñiz Damikolas is hoping to face Republican incumbent Young Kim in November. Kim herself was one of the few Republican women who won in 2020 when she flipped California's 39th District by less than 5,000 votes Due to redistricting, Kim ran in the 40th District in 2022, where she won by a much larger margin. Still, this region of California is in flux demographically and politically, so it makes sense as a target for Democrats. EMILY's List is backing Muñiz Damikolas, but to advance to November, she'll need to get past fellow Democrat, retired fire Capt. Joe Kerr, first, who has been endorsed by the Congressional Progressive Caucus PAC.

Next, in Texas's 15th District, small business owner Michelle Vallejo is favored to advance tonight to a rematch against Republican incumbent Rep. Monica De La Cruz. Vallejo, who has endorsements from EMILY's List and the DCCC, lost by nearly nine percentage points in 2022, but Democratic groups have invested more in the race this time around as a top pickup opportunity. And in California's 3rd District, wildfire specialist Jessica Morse is running to face the Republican incumbent, Rep. Kevin Kiley. Morse is endorsed by EMILY's List, but not the DCCC. She and Kiley are likely to advance out of today's top-two primary, which includes a third-party candidate.

In addition to these, there are several bluer districts with incumbent-less primaries today where Democratic women will be competitive:

- Rep. Colin Allred is running for Senate, opening his seat in Texas's 32nd District. State Rep. Julie Johnson has support from EMILY's List and seems to be one of the top two candidates in a crowded Democratic primary.

- Rep. Tony Cárdenas announced his retirement in his blue San Fernando Valley district (California's 29th). Luz Maria Rivas, who has support from EMILY's List and the Congressional Progressive Caucus PAC, should finish in the top two today.

- Rep. Barbara Lee isn't running for reelection in California's 12th District, instead vying for the Senate. Organizer and civil rights activist Lateefah Simon is a clear front-runner. She has Lee's endorsement, as well as Gov. Newsom's, and backing from EMILY's List.

- Rep. Anna Eshoo announced her retirement after three decades in Congress, opening up California's 16th District. EMILY's List is backing former Stanford dean Julie Lythcott-Haims, but she's caught in a tight race with four other strong candidates who have her beat on the spending front.

- Rep. Katie Porter is also running for Senate instead of reelection in California's 47th District. Lawyer Joanna Weiss, who has an endorsement from EMILY's List, looks to be in a contentious race with state Sen. Dave Min to become the Democratic flagbearer this fall.

Given that Lee, Eshoo and Porter are women and not all of today's female candidates are favored to advance, today's races mainly give Democratic women a chance to maintain the progress they've made in recent cycles.

—Meredith Conroy, 538 contributor