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 the Super Tuesday results come in, there will be a lot of attention to how they compare with the 2016 primaries. In early voting states such as Iowa and New Hampshire, Trump has tended to do better in the places where he did well eight years ago. But we should be careful not to overstate the continuity. While Trump was seen as a relatively moderate Republican back in 2016, he now anchors the conservative end of the political spectrum.

In January 2016, Diana Mutz and I asked a population-based panel of Americans 26 and older whom they supported in the GOP presidential primary. Back then, Trump's best group of GOP primary voters were actually those who called themselves "moderates," while Ted Cruz won respondents who said they were "extremely conservative." Later that year, we asked all respondents to place Trump on a 7-point ideology scale, where "1" meant "extremely liberal" and 7 meant "extremely conservative." Trump scored 5.0, placing him almost exactly at "slightly conservative."

But after Trump had been president for three years and had overseen major tax cuts and an effort to repeal the Affordable Care Act — not to mention being the face of a growing contingent of MAGA-inspired conservatives — perceptions of him had changed. In January 2020, our panelists rated him a 5.6, meaning they saw him as closer to "conservative" than to "slightly conservative."

Other data reinforces the idea that perceptions of Trump continued to shift, and that he shed the perception of being a moderate. In April 2021, I teamed up with Hans Noel to ask political activists who was more conservative among pairs of prominent politicians. From those comparisons, we generated perceived ideology scores. By then, Trump was perceived by all respondents to be fairly far on the conservative end of the spectrum, with just ten GOP politicians to his right versus 43 to his left. (The Republicans who were perceived to be on his right are generally seen as Trump allies, such as Sens. Tommy Tuberville, Josh Hawley and Tom Cotton.) It's noteworthy that at the time, Nikki Haley was ranked just two slots less conservative than Trump.

Noel and I replicated the analysis in November 2023 in a YouGov survey of American adults. Among Republican survey respondents, Ron DeSantis was thought to be the second most conservative figure, with only Ted Cruz viewed as more conservative. But Trump was also far on the conservative end of the spectrum, ranking fifth out of 23 Republicans on the list. It's no surprise that in that same survey, Trump's best group for the primary was respondents who called themselves "very conservative."

Haley, by contrast, had come to be seen as closer to the center of the GOP — she was viewed as more conservative than Mitch McConnell, Chris Christie and Kevin McCarthy, but also more liberal than fellow primary candidates Vivek Ramaswamy and Mike Pence, and Trump allies like Hawley and Sarah Huckabee Sanders. Haley's best group in the November survey was self-described "moderates," although Trump still won that group with 51 percent compared to Haley's 18.

That reflects the fact that DeSantis and Haley cut somewhat different profiles among GOP primary voters. While Haley is the Trump challenger still in the race, DeSantis seems to have been the bigger threat to the conservative base that Trump has come to rely on. And with DeSantis out of the race, Trump has been able to consolidate the GOP's conservative wing, which has increasingly been defined by his politics since 2016.

—Dan Hopkins, 538 contributor