As the democratic presidential field thinned to two frontrunners, Americans took to the polls in six key states: Idaho, North Dakota, Michigan, Mississippi, Missouri and Washington.
How did Bernie Sanders and Joe Biden fare?
Here's a look:
1. It's now Biden's race to lose
After an impressive Super Tuesday finish, Biden transformed his momentum into victories on Tuesday in Mississippi, Missouri, Michigan and Idaho. The remaining states were too close to call at time of publication, but Biden showed promising results in both.
It's not a lot in terms of delegates (there were only 352 up for grabs), and Tuesday's results still haven't landed him the 1,991 needed to secure the nomination.
But it's enough for pundits and the public alike to see the shifting narrative.
Biden himself seems to be kicking his campaign into general election gear. He shook up his standard stump speech by injecting subtle jabs not at his one legitimate primary opponent, but at Donald Trump.
"We need leadership that's honest, truthful, trusted and steady," he said.
"Winning means not only having a president who knows how to fight but how to heal."
2. Sanders lost his 2016 steam
Two of the most devastating blows for Sanders came from Missouri and Michigan, two states where he secured surprise victories against Hillary Clinton in 2016.
Sanders was especially counting on a victory in Michigan, a Midwestern state that prides itself on being blue collar and ultimately voted for Trump in 2016.
This was the one place where Sanders was looking to affirm the core message of his campaign: he's the best choice for America's working class.
The state went for Biden 52 to 47, a sign that it's changed its mind on Sanders in the four years since his narrow 49-48 triumph four years ago.
3. Call it old-fashioned, but key demographics still matter
Early exit polls suggest that Biden's success on Tuesday can be traced back to his popularity with demographic groups that traditionally vote for Democrats, namely African-Americans and suburban voters.
In Mississippi, a state where 40 per cent of the Democratic electorate is African-American, Biden won close to 85 per cent of the African-American vote.
In Michigan, he won overwhelmingly in the suburbs, where Trump won over moderate and swing voters in 2016 but the Republican Party lost at the 2018 midterms. The fact that that group of voters is still showing up for a moderate candidate won't go unnoticed by the Democratic establishment.
Meanwhile, Sanders failed to spark significant turnout amongst millennial and Gen Z voters despite long claiming that one of his top traits as the Democratic nominee would be his ability to inspire those voters to show up on election day.
4. US politics can't escape coronavirus either
Both Sanders and Biden cancelled rallies on Tuesday, citing coronavirus concerns.
Instead of a grand victory speech, Biden held a sombre address for a small number of his supporters and the network television cameras. Sanders didn't speak at all.
As cases in the US spike (along with attention on the Trump administration's response), it's likely that politics will fade into the background for many people suddenly confronted with how to best protect themselves during the outbreak.
It seems unlikely that either Sanders or Biden, or the President for that matter, will be able to conduct the normal activities of a campaign. Especially given the risk to the candidates, who are all in their 70s.
The true impact of the coronavirus on the US election is impossible to predict. The only thing we can say for sure is that it's only just begun to leave a mark.
5. The audience won't be at the debate. The pressure will be
Before results were announced, host network CNN made the decision to hold the next debate — on Monday AEDT — without an audience.
It was already promising to be a strange debate, much closer to the presidential tit-for-tats we'll see later in the year than the all-in-brawls we've watched so far.
But in light of these results, expect a bitter battle between Biden and Sanders, who've both played it fairly cautious on the stage so far.
The Sanders campaign is suggesting that caution will be thrown to the wind this time around. In many ways, this debate is Sanders's last-chance saloon.
But like a sitcom without a laugh track, a debate without an invested live audience will be a strange spectacle. Sanders could land a hundred punches, but will they resonate with TV viewers without the cheers and jeers a live audience provides?
Catch up on all the election action in our blog below
