On Monday, former 2020 presidential candidate Julián Castro announced his endorsement of Sen. Elizabeth Warren (D-MA) for president.

“Elizabeth and I share a vision of America where everyone counts. An America where people⁠—not the wealthy or well-connected⁠—are put first. I’m proud to join her in the fight for big, structural change,” Castro wrote in a tweet with his endorsement video.

The former Housing and Urban Development secretary’s backing of Warren comes less than a week after he dropped out of the race on Thursday. However, his endorsement of the senator isn’t surprising. While campaigning for the Democratic nomination, Castro, who was the only Latino presidential candidate, and Warren often shared public compliments about each other’s policies and ideas.

With Castro no longer in the race, CNN reports that several of his campaign staffers have moved to Warren’s team.

The politician, who was the mayor of San Antonio, Texas from 2009 to 2014, also plans to campaign for the Democratic frontrunner, with rally stops planned for the coming weeks and months. His first stop with the candidate is expected to take place on Tuesday in Brooklyn, New York.

Castro’s support marks one of Warren’s most high-profile endorsements.