HOUSTON — Former vice president Joe Biden brought his resurgent campaign to delegate-rich Texas on Monday, gaining the backing of one-time rivals Pete Buttigieg and Amy Klobuchar amid an avalanche of endorsements as he sought to turn the momentum of his big South Carolina primary victory into success on Super Tuesday.
The day before voters here and in Massachusetts, California, and 11 other states head to the polls, moderate Democrats publicly rallied behind Biden in hopes he could stop progressive Vermont Senator Bernie Sanders, the race’s front-runner, from amassing an insurmountable lead in delegates needed to win the nomination. Biden’s campaign sent out news releases almost hourly all day touting new endorsements from state and federal lawmakers, party elders such as Harry Reid, the former Senate majority leader, and influential Democratic figures including Victoria Reggie Kennedy, the widow of the Senator Edward M. Kennedy.
“I am here heart and soul,” Biden told an energetic crowd at Texas Southern University Monday, receiving the loudest cheers as he touted his strong alignment with minority communities and his ties to former president Barack Obama. “I take nothing for granted, nothing at all. I am asking you for your vote.”
“You got it,” a woman shouted from the overlook of the second floor.
The lively audience at the historically Black university in South Houston was in sharp contrast to those in earlier voting states, where Biden’s campaign sputtered before bouncing back with a landslide victory Saturday over Sanders in South Carolina.
The big win led fellow moderate Buttigieg, the former mayor of South Bend, Ind., to drop out of the race Sunday night. Klobuchar, the Minnesota senator and another centrist Democrat, followed suit on Monday even though she was leading polls ahead of Tuesday’s primary in her home state. They joined other establishment Democrats coalescing around Biden as the favored challenger to Sanders as another moderate, former New York City mayor Mike Bloomberg, appeared on the primary ballot for the first time on Super Tuesday.
Buttigieg announced his support at Biden’s side in Dallas Monday night. Texas will award the second-most delegates on Tuesday, when about a third of all Democratic convention delegates will be up for grabs.
“We need a politics that is about decency, a politics that brings back dignity, and that was what we sought to practice in my campaign," Buttigieg said. "That’s what Joe Biden has been practicing his entire life.”
Klobuchar endorsed Biden at a rally in Dallas later Monday.
“If you feel tired of the noise and the nonsense of our politics, and if you are tired of the extremes, you have a home with me, and I think you know you have a home with Joe Biden,” Klobuchar said standing next to Biden on stage. Later at the rally, Biden got the endorsement of former Texas representative Beto O’Rourke, who dropped out of the presidential race last fall.
After taking jabs at Biden at a Sunday rally in San Jose, Calif., Sanders steered clear of such criticism at a Salt Lake City rally on Monday, instead sticking to his stump speech underscoring proposals for universal free health care, free college tuition, and overhauls of nationwide marijuana and gun safety laws.
“What this campaign is about … it’s more than winning the Democratic nomination, and it’s even more than defeating Donald Trump,” Sanders said before heading to another rally in Minnesota. “What this campaign is about is us, not me.”
On Monday, Bloomberg was the only Democratic candidate to speak in person at the annual conference of the American Israel Public Affairs Committee, a pro-Israel lobbying group, in Washington, D.C. Biden made a video appearance and Sanders boycotted the event. Senator Elizabeth Warren, the other major candidate left in the race, was scheduled to give a speech in East Los Angeles recognizing the Justice for Janitors movement.
Sanders has a big lead in the polls in California, which will award by far the most delegates Tuesday, and also leads in recent polls in Texas and Virginia. He is neck-and-neck with Warren in her home state of Massachusetts and is running close to Biden in North Carolina. Biden’s campaign organization has been criticized by Democrats and has lacked the extensive ground game of Sanders. Biden also has been vastly outspent on advertising in Super Tuesday states by Sanders and particularly Bloomberg, the billionaire who has pumped more than $500 million of his own money into his late-starting campaign.
But Biden has seen a jump in fund-raising as his presidential bid was revitalized in South Carolina. Biden campaign officials said they raised $1 million between 9 p.m. and midnight when Buttigieg left the race Sunday, bringing their weekend total to about $6 million.
Calling Texas the largest and most critical battleground state, Carol Alvarado, who serves in the Texas Senate and endorsed Biden on Sunday, said Democrats here had the greatest chances to beat Trump, even win control of the Texas House of Representatives and turn the state blue in the presidential election with Biden leading the ticket.
“There is a lot at stake,” Alvarado said in an interview at Texas Southern University. “We witnessed on Saturday a resurrection of his campaign and people who are practical want to win.”
Still, with roughly half of Texans and 40 percent of Californians likely to have already cast their ballots during the early voting period, political analysts sought to taper expectations on Biden’s Super Tuesday performance, saying it was hard to make up ground so close to primary day.
But Ed Espinoza, who as executive director of Progress Texas has been working to turn the state Democratic, argued there was still “a lot left of the vote to be cast.”
“There is a lot of love for Biden right now, but I would reframe it,” he said. “It is not so much rallying around Biden, as it is rallying around Black and brown voters.”
In Houston on Monday, Biden sought to capitalize on his support from Black voters as he underscored his close relationship with Obama and highlighted his wins in largely Black South Carolina districts, saying, “I stand here today because of minority communities.”
As news spread among rally goers that Klobuchar had dropped out of the race, some attendees rejoiced.
“One of the biggest hurdles for Biden is the split of moderate voters, and I feel like a lot of people who were going to vote for Pete will go to Biden,” said Laura Herbert, 50, a social worker from Houston.
Charles Drayden, 62, a Houston attorney, said the momentum for Biden started to build when he scored the endorsement of Representative Jim Clyburn, the powerful South Carolina Democrat who gave Biden his prized imprimatur three days before that state’s primary.
“Let’s just say Clyburn is well-known,” he said.
Diehard supporters said they had remained unfazed after Biden’s poor showings in Iowa, New Hampshire, and Nevada, pointing to his efforts to fund historically Black colleges and universities, expand affordable health care, and defend Obama’s legacy.
Mitch Colvin, who is serving his second term as the second Black mayor of Fayetteville, N.C., said Biden’s win in South Carolina changed the game in his state.
“It would have been very difficult to convince people that he was a viable candidate if he hadn’t had a good showing in South Carolina,” he said.
North Carolina State Representative Billy Richardson endorsed Biden on Sunday then campaigned with him and Clyburn in his hometown of Fayetteville. He said he briefly considered endorsing Bloomberg but was concerned about his treatment of women after allegations of sexual harassment. After Biden did well in South Carolina, he believed the former New York City mayor should drop out and put his vast personal fortune behind Biden.
“I think there is a paradigm shift, I really do, I think he’s going to really shake things up,” Richardson said about Biden’s newfound success. “People are going to look back in history and say that’s when he found his voice.”
Globe correspondent Syd Stone contributed to this report.