SAN ANTONIO — Lingering around after Julián Castro announced his presidential campaign here Saturday, Santa Garcia Rivera and her niece, Santa Garcia Reyes, said they were thrilled to see someone from the city's hardscrabble West Side reach for the highest office in the country. But they also expressed some ambivalence as they sized up a potential 2020 presidential field that could include another Texas Democrat: Beto O'Rourke.

"It's really tough," said Garcia Reyes, a 45-year-old education specialist for Early Head Start. "I think they have a lot of the same values."

Ultimately, Garcia Reyes said, "my loyalty is going to be to Julián... just seeing that he's never forgot about the people here in San Antonio." Her aunt, however, seemed less sure which Texan would end up earning her vote if they both run.

Such mixed feelings are not uncommon among Texas Democrats, who could end up with two of their own running in 2020. O'Rourke's closer-than-expected loss to U.S. Sen. Ted Cruz last year made him a national star, eclipsing Castro's longtime status — along with his brother — as Texas Democrats' best hope. Now, all eyes are on whether O'Rourke will ride the momentum to a 2020 bid of his own and officially test the loyalties of people like Garcia Rivera and her niece.

As O'Rourke's 2020 buzz has intensified — with early polls showing him far outranking his fellow Texan — Castro has said there is enough room in the race for both of them. And both have said the other's plans will not affect theirs.

All this is unfolding as delegate-rich Texas is poised to have considerable influence in the 2020 nominating process with its early March primary — a high-stakes moment if the two Texans make can it there.

O'Rourke does not appear to be in a rush to make a 2020 decision and is not expected to make one until February at the earliest. In the meantime, every move he makes is drawing intense attention — from the videos he has tweeted out arguing against President Donald Trump's proposed border wall to his Instagram posts Thursday from the dentist's chair. Media mogul Oprah Winfrey announced Friday that she will interview O'Rourke on Feb. 5 in New York City, an event guaranteed to captivate the political world.

Castro and O'Rourke are not particularly close but have appeared friendly in public, and Castro and his brother, U.S. Rep. Joaquin Castro, D-San Antonio, joined O'Rourke on the campaign trail during the closing weeks of the U.S. Senate race. The brothers' political paths also intersected with O'Rourke's in the first few months of 2017, when Joaquin Castro mulled a U.S. Senate run at the same time O'Rourke did. Joaquin Castro ultimately passed on the Senate bid, announcing his decision about a month after O'Rourke launched his campaign.

Speaking before his brother Saturday, Joaquin Castro said there will be "a lot of great candidates" in the presidential race — many of them friends the brothers respect — "but I know we have the best candidate with the best ideas and the biggest heart." Joaquin Castro told reporters afterward he was not concerned about a potential O'Rourke candidacy.

"All of the candidates who are going to enter this race — there’s something good about everybody, so [Julián]’s just gonna go and do the hard work of focusing on his vision and getting his message out to people," Joaquin Castro said, "and we understand it’s a competition obviously and it’s a race, but you really can’t focus on what other people are doing."

Asked what his message was for conflicted Texas Democrats, Joaquin Castro said, "I would ask them to follow their heart and their mind."

Some Texas Democrats are not waiting on O'Rourke's decision to give their unequivocal backing to Julián Castro. Among them is freshman state Rep. James Talarico, D-Round Rock, who was the first introductory speaker Saturday. Talarico recalled his experience teaching middle school on San Antonio's West Side while Castro was the city's mayor, pushing an education-centric agenda. In an interview afterward, Talarico said it was seeing Castro's leadership "up close and personal in San Antonio" that led him to offer him his "full, complete endorsement for 2020."

"I'm a huge fan of Congressman O'Rourke, he campaigned with me, his campaign was hugely helpful in our race, he would make an incredible president, but just my history has been with Secretary Castro," Talarico said. "No matter who else runs, he’s gonna be my candidate."

Talarico was joined in the lineup by a second state representative, Diego Bernal, a longtime friend of the Castros. And in another show of support among House Democrats, state Rep. Poncho Nevárez of Eagle Pass tweeted Friday that he was "all in" for Julián Castro.

Other Democrats are keeping their powder dry for now, reiterating how much of a net positive it is for Texas to have two Democrats in the 2020 mix.

"I grew up here and never in my lifetime has Texas been a battleground state," said Sri Preston Kulkarni, a former congressional candidate from the Houston suburbs who attended Castro's announcement. "Texas is a battleground state right now, and the energy, the excitement here — to see so many people coming out for a Texas Democrat running for president — that’s huge."

Texas Democratic up-and-comers like Kulkarni face something of a conundrum when it comes to making a decision about who to support in 2020. Castro donated to their campaigns through his Opportunity First PAC and stumped for them. O'Rourke, meanwhile, gave them speaking time at his massively attended events and had an impact on their margins with his closer-than-expected loss at the top of the ticket.

Castro used his Opportunity First PAC to endorse over two dozen candidates last cycle in Texas, including the two biggest winners: Colin Allred, who unseated U.S. Rep. Pete Sessions, R-Dallas, and Lizzie Fletcher, who beat U.S. Rep. John Culberson, R-Houston. Castro was especially involved with Allred, who worked under Castro at HUD, backing him early on in what became a crowded primary.

Allred has not shied away from Castro's 2020 maneuvering in recent weeks, issuing a supportive statement when he formed an exploratory committee a month ago, sending a fundraising email for the committee and talking him up during a recent Sunday show appearance.

"Well, I certainly like my former boss, Julián Castro, who is a friend of mine and a mentor of mine," Allred said Sunday on CBS' "Face the Nation," adding, "we have a lot of political talent in Texas."

For those trying to imagine what it would be like to have both Texas Democrats in the race, Castro's Saturday announcement was instructive. He appeared to speak from a teleprompter, the lineup of introductory speakers was carefully curated to highlight his accomplishments and campaign surrogates were made available to the media afterward — all contrasts with the freewheeling, unvarnished style of O'Rourke's 2018 U.S. Senate run.

To political observers, Julián Castro's announcement speech invoked O'Rourke's 2018 bid in at least one way: Castro vowed not to take campaign contributions from PACs, a hallmark of O'Rourke's run. The promise, which Castro has been making for about a month now, was among the bigger applause lines as he spoke at the West Side's historic Plaza Guadalupe.

Texas Republicans, for their part, were happy to stoke divisions between Castro and O'Rourke on Saturday. On a conference call with reporters before Castro's announcement, Texas GOP Chairman James Dickey said the soon-to-be candidate was "absolutely" grappling with having his spotlight stolen by O'Rourke.

"As someone who made it obvious for a long time that he felt like he had a right to go for the presidency, he’s got to be incredibly miffed at how quickly... the void of absence was filled during the last two years," Dickey said.