SAN ANTONIO – Former Obama Cabinet member Julian Castro joined the 2020 presidential race Saturday as the rush of Democrats making early moves to challenge President Donald Trump accelerates, while anticipation grows around bigger names still considering a White House run.

“I’m running for president because it’s time for new leadership, because it’s time for new energy and it’s time for a new commitment to make sure that the opportunities that I’ve had are available to every American,” he told cheering supporters.

Castro, who could end up being the only Latino in what is shaping up to be a crowded Democratic field, officially kicked off his campaign with a rally in his hometown of San Antonio, where he was mayor for five years. The ex-housing secretary became the second Democrat to formally enter race, after former Maryland Rep. John Delaney.

Sen. Elizabeth Warren of Massachusetts has also started an exploratory committee for president, and four other Democratic senators are taking steady steps toward running. Hawaii Rep. Tulsi Gabbard, the first Hindu elected to Congress, is planning a bid, too.

Castro, the 44-year-old grandson of a Mexican immigrant, made the campaign announcement at Plaza Guadalupe on San Antonio’s middle-class west side, less than 200 miles from the U.S.-Mexico border. The impasse over a border wall that Trump made a central promise of his 2016 campaign has led to the longest government shutdown in U.S. history. Trump was at the Texas border on Thursday to press his case for a wall that he said would help solve a humanitarian and security crisis at the border.

Joining Castro at the campaign kickoff was his twin brother, Democratic Rep. Joaquin Castro, chairman of the Hispanic congressional caucus and a frequent Trump critic.

The Democratic field is starting to take shape even though the first primary elections are more than a year away.

Sen. Kamala Harris of California this past week published a memoir , a staple of presidential candidates. Former Texas Rep. Beto O’Rourke is doing little to dim speculation that he might jump into a field that has no clear front-runner.

Castro is aware he lacks the name recognition of potential 2020 rivals or the buzz surrounding O’Rourke, whose flirtations with 2020 have tantalized donors and activists after a close race last year against Sen. Ted Cruz, R-Texas.

But Castro, who has repeatedly dismissed talk that an O’Rourke candidacy would complicate his own chances, has framed the neighborhood and his upbringing as the story of an underdog.

Castro was raised by a local Latina activist. After a brief career in law, he was elected mayor of the nation’s seventh-largest city at 34. It wasn’t long before Democrats nationally embraced him as a star in the making, particularly one from Texas, where a booming Hispanic population is rapidly changing the state’s demographics and improving the party’s fortunes.

Castro delivered the keynote speech at the 2012 Democratic National Convention. Two years later, President Barack Obama picked him to lead the Department of Housing and Urban Development.

He was on the short list of Hillary Clinton’s potential running mates in 2016. During Castro’s trip this past week to Nevada, one state Latino business leader told Castro that he should again be a top contender for vice president if his campaign falls short.

Like other Democrats running, Castro has said he will not accept money from political action committees tied to corporations and unions, and he has sought to introduce himself to voters as a champion for universal health care and affordable housing.