Secretary of the Department of Housing and Urban Development Julián Castro will endorse Democrat presidential frontrunner Hillary Clinton tomorrow at the launch of “Latinos for Hillary” in San Antonio, sources confirm to HousingWire.

Clinton is scheduled to be at Historic Sunset Station at 1:30 p.m. ET for the launch of the campaign group, and sources say Castro will attend and endorse the former Secretary of State in his former hometown.

The event was not on Castro’s formal itinerary for the week, and because the issue is political and did not involve HUD business, HUD declined to comment.

Sources close to the campaign though confirmed that Castro will attend and will make his formal endorsement.

Castro’s twin brother, Joaquín Castro, says the HUD secretary fully supports Clinton, but stopped short of making it official.

“My brother is proud to support Hillary he believes that she would make the best president of the United States, Democrat or Republican. So he's going to do everything that he can of course to help her win,” Joaquín Castro told media outlets earlier in the week.

Castro took over HUD in July 2014, inherited a troubled HUD rife with allegations from the HUD Office of Inspector General of rampant misconduct and ethical violations.

Castro has been touted as the “Hispanic Obama” after he gave a well-received speech at the Democratic National Convention in 2012, and is considered by many political insiders to be on the vice presidential nominee short list.

Should Castro be tapped for the number two position, he could bring housing policy to the forefront in this election.

(Related: Presidential hopefuls and housing policy experts are set to tackle housing policy at a bipartisan housing summit on Friday.)

Castro formerly served as mayor of San Antonio, a largely ceremonial position in the strong-manager style city government.

He has focused on affordable housing issues since taking the helm at HUD last year.

RNC Director for Hispanic Media Ruth Guerra wasn’t flattering in her reaction to the potential endorsement.

"Hillary Clinton and Julián Castro have one thing in common: no one has any idea what they've accomplished," Guerra said in a statement. "This endorsement will do nothing to save Hillary's flailing campaign in the midst of plummeting poll numbers and an FBI investigation into the mishandling of classified information on her secret email server."

In July, HUD lost one of its senior officials to Hillary Clinton’s presidential campaign.

Betsaida Alcantara, HUD’s assistant secretary for public affairs and one of Castro’s senior advisors, left to become director of media planning for Clinton’s campaign.