Julian Castro, who helped broaden access to pre-kindergarten as mayor of San Antonio, announced last week that he’s seeking the Democratic nomination for president.

Castro also served as secretary of housing and urban development during the Obama administration. In that role, he teamed up with Secretary of Education John B. King Jr. and Secretary of Transportation Anthony Foxx to write a “Dear Colleague” letter encouraging leaders in education, housing and transportation to take action to promote socioeconomic and racial diversity.

In San Antonio, Castro paid for his pre-kindergarten program in part through an increase in the city’s sales tax, which voters approved in 2012. The initiative included professional development for pre-kindergarten teachers, who got the chance to work with a master teacher, as well as monthly workshops for informal caregivers, including grandparents.

In a speech announcing his candidacy, Castro touted that program, and said as president, he would again champion expanding access to early-childhood education.

“As mayor I challenged voters to raise the sales tax to expand high quality full day pre-k for thousands of San Antonio four-year-olds,” Castro said. “We called our initiative Pre-K for SA. Today we live in a world in which brain power is the new currency of success. Everybody counts in this country. Here in San Antonio, I made pre-k for S.A.happen. As president, I’ll make pre-K for the U.S.A. happen!’

Castro has sought to frame his support for expanding early-childhood education and college access in economic terms.

“You can’t be pro-business unless you’re pro-education,” he said in giving the keynote address at the 2012 Democratic National Convention, his biggest national platform to date.

Also joining what’s shaping up to be a crowded Democratic field: Rep. Tulsi Gabbard, D-Hawaii. She’s sponsored legislation to improve outcomes for Native Hawaiian kids and has co-sponsored bills aimed at beefing up school safety and college access.

Castro and Gabbard join a crowded field that includes Sen. Elizabeth Warren, D-Mass. Get a breakdown of the education records of likely candidates here.

Former San Antonio Mayor and Housing and Urban Development Secretary Julian Castro, front left, waves as he arrives with his family to an event where he announced his decision to seek the 2020 Democratic presidential nomination on Jan. 12, 2019, in San Antonio. --Eric Gay/AP

House Speaker Nancy Pelosi of Calif., administers the House oath of office to Rep. Tulsi Gabbard, D-Hawaii, during a ceremonial swearing-in on Capitol Hill in Washington on Jan. 3, 2019, during the opening session of the 116th Congress. --Jose Luis Magana/AP