U.S. Housing and Urban Development (HUD) Secretary Julián Castro followed his twin brother's footsteps and endorsed Hillary Clinton for U.S. president.

Coinciding with Clinton's San Antonio, Texas, trip, the Democratic presidential front-runner held a rally where Castro officially endorsed the former secretary of state to be the next president.

Earlier, however, Castro appeared on MSNBC and explained why he waited to endorse Clinton.

"I've long admired Secretary Clinton but just over a year ago I started my job at HUD and for the last 14 months I've really been focused on my work at HUD and I continue to do that but of course the campaign is getting going and I wanted to make sure to lend my support to the person that I believe would make the next president -- next," said Castro.

Castro said he has respect for Vice President Joe Biden, who has yet to decide his intention for the Democratic Party's presidential nomination, but maintained support for Clinton based on a long relationship he's had with her and former President Bill Clinton.

Castro has been considered as a potential vice presidential pick for Clinton. During an interview with Texas Democratic Party Chairman Gilberto Hinojosa for Latin Post's "Turnout" series in late August, the HUD secretary was considered as the top name to be a vice presidential candidate. Hinojosa said the addition of a name such as Castro on the Democratic presidential ticket will increase voter turnout significantly, especially among the swing states.

"There's no person that we've had in the last 30 to 40 years more qualified than Julián Castro to be a vice presidential candidate," Hinojosa told Latin Post. "That's an example of where Latinos are expecting the Democratic Party to remember how Latinos vote and reach out to them by placing someone on the ticket that they can relate to."

Following Castro's official endorsement, the Republican National Committee's Hispanic Media Director Ruth Guerra said the former San Antonio mayor is more focused on his branding than governance.

"Julian Castro is another ethically-challenged politician who is more concerned about self-promotion than governing," Guerra said in a statement. "With a record of unknown accomplishments, sketchy personal finances and misuse of taxpayer dollars, Julian Castro's endorsement will do nothing more than remind voters of Hillary's similar record of scandals that have nearly toppled her campaign."

Castro was the first Latino to deliver the Democratic National Committee keynote address. His brother, Joaquin, currently serves as the congressman for Texas's 20th Congressional District.

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For the latest updates, follow Latin Post's Politics Editor Michael Oleaga on Twitter: @EditorMikeO or contact via email: m.oleaga@latinpost.com.