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

We won't be paying much attention to Democratic presidential primaries tonight given everything else going on and the fact that Biden is going to win them all. But in the absence of any other results thus far, I am compelled to inform you that ABC News is projecting that Biden has won the Iowa primary.

(And yes, it is a party-run primary, not a caucus, despite what the Iowa Democratic Party will tell you! As you'll recall, after their debacle in 2020, Iowa Democrats got demoted from their usual first-in-the-nation placement on the calendar, and as a result they no longer hold caucuses in the traditional sense. Instead, the election was conducted entirely by mail by the state Democratic Party.)

—Nathaniel Rakich, 538

One thing I'll be watching tonight is how a handful of endangered incumbents fare in their primaries. In Alabama's 1st District, we're actually guaranteed to see an incumbent lose — because there are two of them running! Due to a court-ordered redistricting last year, Reps. Barry Moore and Jerry Carl are facing off in a chippy Republican primary that's seen Carl call Moore a "tax cheat" and Moore's allies call Carl a member of the "crazed left."

In Texas, the most endangered incumbent tonight might be 15-term Democrat Sheila Jackson Lee in the 18th District. Jackson Lee faces a spirited challenge from former Houston City Councilwoman Amanda Edwards, who jumped into this race when Jackson Lee ran for mayor of Houston last year, and didn't jump out after the congresswoman lost and decided to seek reelection. Edwards has outspent the incumbent two-to-one and one public poll showed the race neck-and-neck. In the 7th District, fellow Houston Democrat Lizzie Fletcher looks much better positioned against her primary challenger, Pervez Agwan, who hasn't gained much traction in his campaign to run to Fletcher's left on Israel issues despite spending over $1 million.

Texas Republican Tony Gonzales also has his hands full in the 23rd District, with several challengers looking to keep him under the 50 percent threshold necessary to avoid a runoff. The most prominent of those opponents is probably YouTuber and gun activist Brandon Herrera. Gonzales was censured by the state GOP after he voted in favor of a gun safety measure in Congress.

And in California, national Republicans are racing to prevent 22nd District Rep. David Valadao from falling out of the top two in the primary for his swing seat. The Congressional Leadership Fund has spent more than $1 million boosting Valadao and attacking Republican Chris Mathys, who would be a much weaker general election candidate but came up just 1,220 votes short of beating Valadao in the 2022 primary. Democrats, meanwhile, are spending big in this race to prevent both Republicans from securing the top two spots and locking out their top pick, former state Assemblyman Rudy Salas.

—Jacob Rubashkin, Inside Elections

California, a state known for having a lot of ballot initiatives, has only one statewide proposition on the ballot today: Proposition 1>), a measure that would expand funding for substance use disorder and mental health treatment and programs, including housing support. Pre-election surveys suggest the measure will pass overwhelmingly: in an average of polls conducted since January 1, 61 percent of voters support the measure, while 31 percent oppose it.

—Mary Radcliffe, 538