It's Super Tuesday, the closest thing the U.S. has to a national primary election. What was expected to happen in 14 states and the territory of American Samoa got a big shakeup in the past two days as Pete Buttigieg and Amy Klobuchar suddenly dropped out of the race and endorsed former Vice President Joe Biden.
The move was seen as an effort for Biden to reel in the more progressive Sen. Bernie Sanders, who has the delegate lead going into Tuesday. Sanders was in line for the largest portion of the more than 1,300 delegates up for grabs, but the last 48 hours may have changed all that.
This is also the first time former New York City Mayor Mike Bloomberg will be on the ballot after having spent about a half-billion dollars in advertising. And Sen. Elizabeth Warren is showing no signs of leaving even as she has struggled in the first four contests.
Here are five things to watch for Tuesday.
Will the Biden endorsements make an impact?
The fact that two of the top six remaining candidates in the presidential race suddenly dropped out just before the biggest primary day of the season can't be understated. That they both endorsed their rival on the eve of Super Tuesday is also unusual.
Will the impact of this be seen immediately? Will their voters have gone to Biden Tuesday? We may need to wait for exit polling to find out.
Part of the issue is that many states have early voting, so millions of people already cast their ballots for Buttigieg, Klobuchar, or for Tom Steyer, who bowed out Saturday. And while some of their supporters voting Tuesday may run to Biden, there is no guarantee some won't move to Sanders, Bloomberg or Warren.
But Biden also got a potential endorsement boost Monday from former presidential candidate Beto O'Rourke in the ex-congressman's native state of Texas, the second-largest delegate prize.
How big is Sanders' California delegate haul?
You'd be hard-pressed to find any polls that have someone not named Bernie Sanders winning California Tuesday, which has the most national delegates at stake -- 415. But what looked like a potential runaway is likely to be blunted as Biden picks up more votes from Buttigieg and Klobuchar supporters.
The number to watch is 15%. That's the percentage of votes needed to achieve viability in any of these primary contests. If Biden gets over that number statewide, he will get a share of the statewide delegates. If he doesn't, expect Sanders to have a runaway night. Some recent polls had Sanders as the only candidate getting over 15%, but that was before everyone started dropping out.
Will Bloomberg's $500 million gamble pay off?
After rising in the polls into mid-February, buoyed by hundreds of millions of dollars in advertising, the billionaire tailed off following his two debate performances.
Barring a surprise, polling shows Bloomberg is not likely to win any states Tuesday. He is in the moderate lane with Biden, so he could pull voters from the former vice president in other places -- perhaps keeping Biden from that 15% viability in some states.
Bloomberg joined the race late last year when it looked like Biden might be faltering. A bad night for Bloomberg could turn this into a short-lived candidacy to avoid pulling votes from the resurgent Biden.
Is Warren all-in to the convention?
Polling indicates the only place Warren has a chance to pull off a win is in her home state of Massachusetts. But Sanders has been surging there in recent days and held a rally in Boston over the weekend with an estimated 13,000 people attending.
There have been calls from both Biden supporters and Sanders supporters for her to get out of the race, although Warren hasn't dropped any hints she plans to do so. A Morning Consult poll taken last week shows 40% of Warren voters have Sanders as their second choice. But a combined 44% named Biden, Buttigieg or Klobuchar as choice No. 2.
At a rally in Los Angeles Monday, Warren went after Biden, saying a “Washington insider will not meet this moment,” nor will nominating a man “who says we do not need any fundamental change in this country,” according to The Associated Press. She didn't mention Sanders by name, but said voters still have more than two choices.
Who is seen as the front-runner after Tuesday?
If Sanders can pull off the Super Tuesday results that many expected before Biden's South Carolina win and sudden consolidation of support, he can potentially re-take the narrative.
But if Biden makes it a competitive night and keeps the delegate count within reach -- say 100 -- or even has the lead by the end, it will give him momentum headed into the next rounds of contests and almost assuredly put the race on the path to a brokered convention in July.