Democrats are dropping out and backing Joe Biden. But he faces a tougher test on Super Tuesday.

South Carolina jolted the Democratic presidential contest by giving new life to Joe Biden’s campaign as he challenges the front-running Sen. Bernie Sanders.

Biden’s moderate rivals are throwing their support behind him. Sen. Amy Klobuchar quit the race Monday and endorsed Biden at a rally Monday night, along with Pete Buttigieg, who dropped out late Sunday. Their decisions could consolidate Biden’s support among more centrist voters and those who fear Sanders is too far to the left to beat President Donald Trump.

But another test, with potential new twists, arrives Tuesday.

Before the remaining candidates have even caught their breath, 14 states will vote in Super Tuesday contests that could reinforce Biden’s rise, swing energy back toward Sanders, or throw in another wrinkle, as billionaire Mike Bloomberg appears on the ballot for the first time.

Biden’s blowout victory in Saturday’s South Carolina primary gave him an opening to become the singular moderate alternative to Sanders and his sharply liberal agenda. But the former vice president’s surge could be short-lived if he can’t muster the resources and organization to match Sanders’ broad and deep grassroots support, or if Bloomberg wins a chunk of the centrist vote after months of saturating the airwaves with television ads in multiple states.

A slew of current and former Democratic senators, governors, and House members from California, Virginia, and North Carolina also rallied behind Biden in the hours after his South Carolina victory.

“He has the experience necessary to achieve progress and deliver results, and the ability to unite our party’s broad coalition and lead us to victory in November,” Rep. Don Beyer (D., Va.) said late Sunday, hours after Buttigieg dropped out. Beyer had supported Buttigieg, the former mayor of South Bend, Ind.

Biden’s campaign, which has far less money than those of Bloomberg or Sanders, is counting on the momentum from South Carolina to carry him in states where he has far less staff. He hopes to prove his big win wasn’t a one-off.

Southern states voting Tuesday also have sizable African American electorates, but none as large as that of South Carolina, said Kyle Kondik, an elections analyst at the University of Virginia’s Center for Politics.

“He has to show strength in the North and the Midwest to really threaten Sanders, I think, and that’s assuming he holds the South, and that’s not a guarantee,” Kondik said. “There are more questions about Biden’s viability than there are Sanders'.”

But, pointing to the decisions by Buttigieg and Klobuchar, he added, “What we’re seeing now is the start of this sort of formal stop-Sanders movement.”

Super Tuesday presents a different measure than the four states that have voted so far.

For the first time, candidates will compete across multiple states on one day, testing their organizational abilities and their appeals across a broad spectrum of Democratic voters all at once, in what amounts to a national primary.

While in the first four contest outcomes largely rested with distinct demographic groups (white voters in Iowa and New Hampshire, Latinos in Nevada, African Americans in South Carolina), Super Tuesday voting will range from heavily black electorates in the South to significant Latino blocs in California and Texas and white suburban voters in Virginia. More than one-third of the total delegates needed for nomination are up for grabs on Tuesday.

» READ MORE: Live from East L.A.: How the Latino vote became the secret weapon for ‘Tío Bernie’ | Will Bunch

Biden, who fared best in South Carolina with older black voters and white moderates, according to exit polls, is aiming to win big again on Tuesday with similar voters in other Southern states and in suburban areas across the map.

Sanders is targeting the huge delegate hauls in California and Texas — both places where he may capitalize on his strength with Latinos.

One example of that strength was Carolina Ramirez of Greenville, S.C., who has volunteered for the Sanders campaign since 2016, when she was 16. She wasn’t involved in politics before, but felt a personal connection to his immigration policies: She has friends and relatives who are undocumented immigrants.

“My vote isn’t just for me, I’m doing it for them, I’m giving them a voice, and I think a lot of Latinos feel that way,” Ramirez said.

» READ MORE: Bernie Sanders is surging with Latinos. But Mike Bloomberg might have hidden appeal in Pa.

Sanders has built the most devoted and enthusiastic following, and while they represent just a fraction of the Democratic electorate, that could be enough if his rivals continue to splinter the rest of the vote.

Meanwhile, Sen. Elizabeth Warren is fighting to show she has life left in her campaign. She hasn’t finished better than third place in any of the early contests, and badly trails Sanders and Biden in the race for delegates.

Much will hinge not only on who wins each state, but by how much, since the Democratic delegates are doled out roughly proportionately to the vote in each. A blowout win for Sanders in California could leave him in a commanding position. A close call combined with more Biden romps in the South might suddenly make it into a two-person race.

» READ MORE: A progressive movement sweeping through counties Trump won in Pennsylvania could help Bernie Sanders win

Biden’s victory in South Carolina provided his supporters hope in part because he showed strength, in that contest at least, with a broad group of Democrats.

While he tends to poll better with older voters, in South Carolina he narrowly beat Sanders among those ages 17 to 29.

Still, there’s a generational drop off for Biden nationally.

Faith Buchanan, a college sophomore from Atlanta, said she doesn’t know many people her age who back Biden. At a Sanders rally Friday in Columbia, S.C., she was surrounded by younger voters.

“If there’s support for Biden among young people, it’s typically people who are a bit less politically aware, I think, and certainly not as progressives,” she said. “I don’t know anyone who supports [Sanders] more than students.”

Conversely, Michael Abrams, a 20-year-old junior at Coastal Carolina University, said at a Biden rally Thursday that he supports the former vice president partly because he sees the support Biden gets from older voters — and takes their experience as a signal they know who can beat Trump.

“Those are normally the ones that really determine elections, and they’ve picked a lot of winners. I think it’s worth listening to that," Abrams said. “I like Bernie Sanders, but feel as though a lot of Bernie Sanders’ policies and procedures, they sound good, but I don’t think they’re really realistic. I think he’s ahead of where America’s at right now.”

If Biden can pull in white moderate voters, black voters, and middle-age to older voters, that’s a robust coalition, said Antjuan Seawright, a South Carolina Democratic consultant.

“You have to keep in mind the constituency in the middle," Seawright said. “A grandmother and granddaughter may see things differently. But I think the mother in between that is more in line with the grandmother than the daughter.”