Despite Castro's endorsement of Warren, some of his supporters have splintered

About two weeks into his tenure on Sen. Elizabeth Warren’s presidential campaign, nearly a dozen of former presidential candidate Julian Castro's supporters from his home state of Texas, a delegate-rich state that will play a significant role on Super Tuesday, have splintered in the wake of his endorsement for her, sparking questions about his pull among the people who supported him — particularly in the Latino community.

Nine of his supporters switched to support one of Warren’s rivals in the top tier, former Vice President Joe Biden, which the Biden campaign touted as a reflection of his “momentum” heading into Super Tuesday, while Castro’s own former deputy campaign manager announced his support for Vermont Sen. Bernie Sanders.

Soon after, the Warren campaign announced that three of the legislators that previously endorsed Castro had decided to follow suit and endorse Warren, along with details of the ground game and staff hires the campaign has steadily built up since the summer.

Democratic Texas state Rep. Armando Martinez was one of the nine legislators to switch his support to Biden, having already decided ahead of time that he would support him if Castro dropped out.

Martinez, who represents part of Texas that runs along the U.S.-Mexico border, and is secretary of the Mexican American Legislative Caucus, said he initially supported Castro because he wanted a candidate who would represent Latinos. But given Castro’s decision to leave the race, he switched his support to the candidate he thinks is most likely to win.

The decision was not about Warren, Martinez said.

“To me, it's not about optics,” Martinez said. “It's about, you know, I feel confident with who I feel I can support and who I want to support. And I'm not going to have anybody tell me otherwise — and my choice is my choice. In other words, it doesn't matter to me who supports who.”

But while the immediacy of Castro’s decision to endorse Warren was “unusual,” according to experts, Castro’s supporters’ decision to go their own ways is not.

“It’s not like this magical power that the candidate has he can just transfer over all of his support,” Melissa Michelson, political science professor at Menlo College and former president of the American Political Science Association Latino Caucus, told ABC News. “The unusual part is that he endorsed Warren so quickly after he dropped out.”

But his quick move also gave the endorsement more potency, given the freshness of his decision to end his bid, especially in places where the vote is less than 30 days out, like Iowa, where some voters attended his first events for Warren there because they’d already supported him.

David Barajas, who attended Castro’s event with Warren in Marshalltown, Iowa, had Castro as his first choice ahead of the Feb. 3 Iowa caucus, but is now actively considering Warren because of the endorsement.

“Sen. Warren has really been somebody, also, from the very beginning that has been really at the top three or four people for me. Him endorsing her really makes a big difference to me,” said Barajas, whose family runs a local bakery in nearby Rock Falls, Iowa.

And on a national level, it also sparked conversation about a possible presidential ticket.

“Maybe he [Castro] thinks that campaigning with her and getting all this chatter going about them being a ticket is something that's going to help raise his profile — and maybe raise hers,” Michelson said. “So, it could be strategic. It could definitely be something about thinking that this is a possible way to make it to the White House.”

But for Democratic Texas State Rep. Oscar Longoria, the safer bet is the man who already had a place on the ticket.

Longoria, who also represents border counties in the state, said he decided to endorse Biden in part because he saw Texas Democrats, and especially Latinos, flourish under the Obama administration.

“When I look at everybody, I just think he seems like the most logical fit,” he said. “Getting somebody that has institutional knowledge and knows the way D.C. works and what needs to happen...I mean, take somebody that understands the process.”

Longoria said he didn’t choose to endorse Warren, or any of the other candidates running, because he fears they “may not be able to beat Donald Trump,” and because he felt other candidates were too far left.

“A lot of the other candidates within the Democratic Party are very polarizing — you know, you either like them or you don’t,” Longoria said.

By contrast, the decision by Castro’s former national deputy campaign manager, Derek Eadon, was largely based on some of those polarizing issues — and his belief that now is exactly the right time to fight for them.

“Bernie is just a little bit more of a fierce advocate on Medicare for All and some of these other issues,” Eadon said, adding that he also supports Sanders’ stance on foreign policy and money in politics.

Eadon said it’s because of Sanders’ being “consistent” on these issues that he thinks Sanders is “the person you want, heading into the general election, to put a fight against Trump.”

Sanders, Eadon said, has netted support from people who have never been interested in politics, perhaps expanding Democrats’ reach in a way that could prove powerful, as well as voters that candidates are already trying to reach.

“You'll see a lot of candidates talking about whether it's, ‘Do we go after kind of working class voters and swing states, or do we go after newer voters in more diverse communities?’ And I think he [Sanders] is the only candidate that actually does both,” Eadon said.

But the ability to further reach voters, Michelson said, is also where a Castro endorsement could benefit Warren. Because of Castro’s former role as the only Latino in the Democratic race, and his family’s immigrant background, he’ll likely attract Latino voters in ways other surrogates can’t, she said.

“What the political science scholarship shows about endorsements is that for Latinos and other communities of color, an in-group endorsement is going to be more powerful,” Michelson said.