Four days after he ended his bid for the White House, Julian Castro endorsed Sen. Elizabeth Warren of Massachusetts for the Democratic presidential nomination.

“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,” the former San Antonio, Texas mayor and Housing secretary during former President Barack Obama’s second term wrote on Twitter Monday.

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Though Castro – who was the only Latino candidate in the large field of Democratic White House hopefuls – tangled a couple of times with former Vice President Joe Biden, he always seemed to have warm relations with Warren.

CASTRO DROPS OUT OF THE 2020 WHITE HOUSE RACE

Warren – who’s considered part of the top tier of nomination contenders along with Biden, Sen. Bernie Sanders of Vermont, and former South Bend, Ind., Mayor Pete Buttigieg – praised Castro and his proposals a number of times on the campaign trail last year.

Short on campaign cash, unable to resonate in the polls, and failing to qualify for the most recent debates, Castro suspended his campaign last Thursday. He’s expected to join Warren at a campaign event Tuesday in New York City.

Some political pundits point to the possibility of Warren – if she wins the nomination – choosing Castro as her running mate.