Housing and Urban Development Secretary Julian Castro is being vetted as a potential running mate for presumptive Democratic presidential nominee Hillary Clinton, according to a Democratic source familiar with the process.

Castro, 41, would be the first Hispanic candidate on a presidential ticket. His selection could help Clinton energize Hispanic voters and sharpen her contrast with presumptive Republican presidential nominee Donald Trump, who has courted controversy with his anti-immigrant proposals and incendiary rhetoric.

Castro delivered the keynote address at the 2012 Democratic National Convention in Charlotte, the same prime-time role played in 2004 by Barack Obama, then an Illinois state senator.

As mayor of San Antonio, Castro led a successful effort to expand prekindergarten in the city. He was tapped by President Obama in 2014 to lead the U.S. Department of Housing and Urban Development.

“At every challenge that has faced Julian Castro, he has knocked it out of the park,” said Christian Archer, a Texas-based Democratic strategist who worked with Castro in San Antonio.

Castro -- whose twin brother, Democratic Rep. Joaquin Castro, represents San Antonio in Congress -- lacks the experience of more seasoned potential running mates such as Tim Kaine, a current U.S. senator and former governor of Virginia, and Rep. Xavier Becerra of California, a top House Democrat.

And unlike Sen. Elizabeth Warren of Massachusetts and U.S. Labor Secretary Tom Perez, Castro is not favored by progressives, who criticized him over federal mortgage policy this spring.

But his supporters say the telegenic housing secretary could help broaden Clinton’s appeal.

“He’s Gen- X, she’s a baby boomer. He brings gender balance, he brings regional balance,” said Henry Cisneros, a former HUD Secretary under President Bill Clinton and former San Antonio mayor.

The inclusion of Castro on the list of potential vice presidential candidates is not unexpected. The Associated Press first reported on June 21 that he was being vetted by the Clinton campaign, along with Warren and Kaine.

As the Clinton campaign reviews his professional and personal records, Castro has continued to play coy.

At the Texas Democratic Convention last month, he told reporters he was not being vetted and downplayed the likelihood of his nomination.

Castro endorsed Clinton last October and campaigned with her around the country through the primary season.

"I am going to really look hard at him for anything because that’s how good he is,” Clinton said of Castro at a round-table in Texas shortly after his endorsement of her.

The Clinton campaign did not respond to a request for comment.