NASA astronauts Jasmin Moghbeli and Loral O'Hara voted in today's primaries ... from outer space. The two have been orbiting the earth aboard the International Space Station for roughly six months, but both still found a way to exercise their civic right.

—Cooper Burton, 538

Four years ago, Super Tuesday was one of the last big news events before the declaration of the COVID-19 pandemic. Just days later, the U.S. and much of the world would go into lockdown in an effort to stem the virus's spread.

As Julia noted, in 2020, Super Tuesday marked the point when the Democratic Party consolidated behind Biden. But I think that, partly because of the pandemic, even close observers of American politics don't appreciate just how unlikely Biden's Super Tuesday comeback was.

This year in Iowa, Ron DeSantis's second-place finish with 21 percent of the vote was enough to effectively end his campaign. But in 2020, Joe Biden came in fourth in the Iowa Democratic caucuses.

Similarly, pundits have viewed Trump as the prohibitive favorite in the 2024 race since at least his New Hampshire victory, when he topped Haley 54 percent to 43 percent. In 2020, however, Biden's New Hampshire performance was far weaker than Haley's this year — he finished fifth in the state, winning just 8 percent of Democratic primary voters.

But in a very short period four years ago, Biden resurrected his campaign. He convincingly won South Carolina on Feb. 29 thanks to his strength with Black voters, who had been few and far between in Iowa and New Hampshire.

Then, both Amy Klobuchar and Pete Buttigieg endorsed Biden in the run-up to Super Tuesday, consolidating the more moderate side of the Democratic Party against Bernie Sanders. That, in turn, positioned Biden for a decisive Super Tuesday win that made him the front-runner in short order. While Sanders won California, Biden won 10 states, including Massachusetts, North Carolina and Texas.

What explains the dramatic change in Biden's fortunes over a few short days leading up to Super Tuesday in 2020? In his book "Learning from Loss," political scientist Seth Masket emphasizes the Democrats' overwhelming aim to defeat Trump, and to find a candidate who gave them the best chance of doing so. At the time, there was evidence that Biden ran better against Trump than other Democrats. Many Democrats were willing to follow the cues of party leaders about their most competitive candidate, and in doing so, they vaulted Biden to the nomination.

In this year's GOP primary, there's some evidence that Haley may be a stronger general election nominee than Trump. But in a late-November survey I conducted via YouGov, GOP voters overwhelmingly saw Trump, not Haley, as their strongest candidate, and there's no evidence that's changed. So on the Republican side, the grounds for a similarly sudden Super Tuesday switch just aren't there.

—Dan Hopkins, 538 contributor

Super Tuesday has over 40 years of history that are deeply entwined with a bunch of issues in the presidential nomination process. The term "Super Tuesday" was first used in 1980 but was promoted by Democrats in 1988 as a deliberate effort to give an advantage to more moderate candidates. This was a direct reaction to the idea that the party's 1984 nominee, Walter Mondale, had lost to Ronald Reagan because he was too liberal. This strategy didn't really work out, though, and Democrats ended up nominating another northern liberal, Michael Dukakis.

In other words, this early attempt at a Super Tuesday brought some of the disadvantages of a regional primary, reducing the amount of attention on individual states and pressuring states to move their primaries earlier without really strengthening the influence of the region. Another drawback was that, by trying to enhance Southern influence by holding contests early, Super Tuesday also contributed to the "front-loading" problem", or the issue of having too many delegates selected at the beginning of the primary calendar.

Over time, Super Tuesday has taken on other significance as an important turning point in the race. As party politics scholar Caitlin Jewitt noted, in 2016, everyone thought that Sen. Ted Cruz needed to do well on Super Tuesday, which was heavily concentrated in Southern states where he needed to rack up wins — and when that didn't happen, it was a significant blow to his candidacy. For Biden in 2020, Super Tuesday marked the point when the party consolidated behind him. And in 2008, Super Tuesday made it clear that the Democratic nomination was a real race between Hillary Clinton and Barack Obama, as neither one scored a decisive victory.

It's hard to know exactly how this will play out in 2024. Republicans don't have the same ideological history with the big primary day as Democrats do. But the potential for a turning point in the race is there: Because so many delegates are at stake today, unless Haley wins a significant share of them, it may not make sense for her to stay in the race after tonight.

—Julia Azari, 538 contributor

Since about the mid-1990s, Democrats have been electing more women to Congress than Republicans, and the difference grows bigger each cycle. This has a lot to do with the supply of candidates — more women identify as Democrats, and the women in the pool of traditionally "qualified" candidates (college-educated, in white-collar professions) are likely to lean Democratic. There's also the issue of demand — Democrats are more than twice as likely (75 percent to 29 percent) than Republicans to agree that there are too few women in politics.

These supply and demand issues may be mitigated if the Republican Party's organizational arm and donor class actively recruited, endorsed and financially backed women in primaries for competitive, or safe, red seats in November. This is the playbook Democratic PAC EMILY's List has been working from for years to elect more Democratic women to Congress and governorships. According to academic researchers, Democratic groups designated to elect more women are more likely to be prioritized by their donors than their Republican counterparts, which helps explain their success.

Although the GOP doesn't have a heavyweight equivalent to EMILY's List (which spends millions each cycle), there are groups committed to electing more Republican women to Congress. A couple of prominent new groups (Winning for Women and Elevate PAC) cropped up after the 2018 election, which elected 42 new women to Congress, but only four that were Republican. As a result, in both the 2020 and 2022 cycles, more Republican women ran in primaries than ever before, according to the Center for American Women and Politics.

But more women running doesn't always translate into more women winning. As we wrote ahead of the 2022 midterm elections, more Democratic than Republican women were nominated to run that year in House and Senate races where their party was either competitive or favored to win. While the GOP may have run and endorsed more women in primaries, it didn't emulate Democrats' strategy of actively recruiting women to run in races where they could win in November.

Today, there are just a few non-incumbent Republican women competitive for nominations in races they'd have any shot of winning in November. In Alabama's 2nd District, an incumbent-less primary due to redistricting, four of the eight Republicans running for the nomination are women. Of those women, attorney Caroleene Dobson has been endorsed by the women-focused VIEW PAC. Neither Trump nor the party committee has endorsed any candidate in that primary, but Dobson faces tough odds winning the crowded primary, and even tougher odds in a general expected to heavily favor Democrats.

11 Republicans are competing in Texas's 26th District, another race with no incumbent. Of two women in the race, Luisa del Rosal, a small business owner and former congressional chief of staff, has been endorsed by VIEW PAC. But she will have to defeat Trump endorsee Brandon Gill (who's also endorsed by the Club for Growth). The Republican woman running today with the most likely path to victory is former Rep. Mayra Flores: she's running to reclaim Texas's 34th District, the seat she won in a 2022 special election but lost in the general election later that year. She is endorsed by both Trump and VIEW PAC, which bodes well for her to face Democratic incumbent Vicente Gonzalez in a competitive general.

—Meredith Conroy, 538 contributor

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