Julián Castro, center right, gets a hug from his twin brother, U.S. Rep. Joaquin Castro (D-Tex.), during an event Saturday announcing his decision to seek the 2020 Democratic presidential nomination. (Eric Ga/AP) (Eric Gay/AP)

Former San Antonio mayor and Obama administration official Julián Castro is running for president on universal prekindergarten, “comprehensive” immigration reform to provide a pathway to citizenship for all undocumented people in the United States and a Medicare-for-all health-care system.

Castro, who announced his presidential bid in a speech in San Antonio on Saturday, has expressed support for several other policy ideas that have become increasingly popular among the Democratic Party’s base — including a higher minimum wage, a “Green New Deal” to combat climate change, and a push for criminal justice reform and reduction in police violence.

Castro grounded his pitches for education and housing in his experience in local and federal politics, and his opposition to President Trump’s immigration policies in his family history. He served as head of the Housing and Urban Development Department under President Barack Obama, and, as mayor of San Antonio, implemented universal pre-K for the city and a program that helps students apply to college.

But outside those areas and unlike most of his primary competitors, Castro does not have a long legislative or voting record on which to draw — or be attacked over. That gives him a freedom to stake out his positions for the first time, an option his opponents may not have, said Lucy Flores, a former Nevada assemblywoman who served as a delegate for Sen. Bernie Sanders’s 2016 presidential campaign.

“As everybody starts to announce their candidacies and plant their flag, Julián really has an opportunity to define himself in a way many of the other candidates don’t,” Flores said. She noted Castro did not express support for free access to public colleges and universities, which many on the left support, but said “this first speech was incredibly progressive and social-justice oriented.”

Conservatives are likely to criticize Castro for pushing expanding federal spending at a time when annual deficits are hovering close to $1 trillion, while some on the left may argue Castro has expressed support for some policies only after those ideas became fashionable, especially compared with his competitors in the Democratic primary.

Castro’s aides say the candidate is likely to release more detailed policy proposals, including on housing and immigration reform, at a later date in the campaign. But here’s a look at some key policy ideas Castro hopes elevates him to the White House.

Universal pre-K: Pushing for every family in America to be able to send their child to prekindergarten is expected to be one of Castro’s major priorities in his bid for the White House, according to current and former aides.

In 2012, San Antonio voters approved Castro’s proposal to create what his staff says is a universal pre-K program — known as “Prek4SA” — in exchange for an ⅛-cent sales tax increase. (Politico said it was not “universal pre-kindergarten, it’s pre-K for disadvantaged kids,” noting it charged high prices for wealthier families.) The plan offers pre-K and free transportation at four centers throughout the city. By July 2018, it had served almost 8,000 students, according to the Texas Tribune.

“Here in San Antonio, I made Pre-K for S.A. happen,” Castro said at his rally. “As president, we’ll make pre-K for U.S.A. happen — universal prekindergarten for all children whose parents want it.”

One body of research, alluded to by Castro in his speech, suggests 3- and 4-year-olds who fall behind in math and reading never catch up if they don’t get formal schooling until kindergarten.

In 2017, only 55 percent of America’s 3- and 4-year-olds attended preschool, compared with 75 percent in China and even higher rates in Germany, Britain and other countries. Spending on preschool as a share of the economy is more than twice as high in Denmark, Spain and Israel, according to a 2013 report from the Center for American Progress, a left-leaning think tank.

Universal prekindergarten would require congressional approval and may be difficult to pass, though its price tag is considerably lower than many other initiatives pushed by Democratic presidential candidates, including Castro. Obama proposed a $66 billion investment in pre-K that White House representatives said at the time would make early education available for all American children, while other estimates suggest the cost of universal pre-K may be lower.

“He’s totally steeped in the early education literature,” said Jamie Castillo, who was Castro’s chief of staff in San Antonio and later worked as assistant secretary for public affairs under Castro at HUD. Castro “thinks of it as the great equalizer. Fundamentally, he believes pre-K to higher ed is a great equalizer in life.”

Affordable college for two years: Castro is also expected on the campaign trail to cite his experience in San Antonio creating the Cafe College, which provides counseling and advice for students seeking to go to college in the city.

“We’ll work to make the first two years of college — a certification program or an apprenticeship — accessible and affordable, so millions more young people and people who are returning to school later in life can get the skills they need to get a good job without drowning in debt,” Castro said.

Part of Castro’s interest in higher education, former aides say, is biographical: Castro was raised by a single mother on the west side of San Antonio before going onto Stanford University and Harvard Law School on his way to the Obama administration.

Sara Goldrick-Rab, a professor in higher education at Temple University in Philadelphia, noted that Castro did not vow to make it so attending public colleges is tuition-free, which is what way Sanders (I-Vt.) did in the 2016 campaign. Goldrick-Rab said she liked that Castro could make the link between housing problems and higher education, as well as his focus on improving the first two years of college, but argued that the candidate’s proposal suffered from the vagueness of 2016 Democratic nominee Hillary Clinton’s messaging on the issue.

“What he said was technocratic, and I’m confused about why he would do that,” Goldrick-Rab said. “The right way to do it is to say, ‘You can go to college without debt,’ and signal a push to tuition-free-for-all or free for those under a certain income cap. But the word ‘affordable’ doesn’t mean anything anymore.”

“Comprehensive” immigration reform: Castro began his speech by noting that his grandmother, Victoria, emigrated from Mexico to Texas when she was 7.

“We say no to scapegoating immigrants and yes to dreamers, yes to keeping families together and yes to finally passing comprehensive immigration reform,” he said.

Castro’s fuller immigration policy platform is expected to be released at a later date. But it will include a path to citizenship for all the about 11 million undocumented people living in the country, a policy broadly within the Democratic mainstream. It will also include an expedited pathway to citizenship for the “dreamers” — young immigrants brought to America as children — as well as changes to “streamline and simplify” America’s asylum process, an aide said.

Medicare-for-all: In his speech, Castro also said he would support a single-payer health-care system, saying Medicare “should be there for everybody” as it was for his grandmother when she was sick. Castro has supported Medicare-for-all at least since at least 2017, according to an aide.

Medicare-for-all is a proposal to move every America to a single government-run insurer that charges no deductibles or premiums. Doing so would massively increase government expenditures — by as much as $33 trillion by 2031, according to one conservative think tank’s estimate — while offering health insurance to the Americans who lack it and preventing millions more from being forced into medical bankruptcy. It would require enormous tax increases to finance, although supporters maintain they would be offset by zeroing out every family’s spending on premiums and deductibles.

Castro has not yet embraced a particular bill or proposal for implementing Medicare-for-all.

Climate change: In his speech on Saturday, Castro said his first act in office would be to recommit the United States to the Paris climate change agreement, in which countries pledged to try to cut their greenhouse gas emissions. Trump pulled the United States out of the accord, signed under Obama, in June 2017.

Castro also expressed support for the “Green New Deal,” a push to restructure the U.S. economy with an enormous public investment in clean energy to stave off catastrophic climate change.

The former mayor declared in his speech that he would not take a “dime” from political action committees, but he has not yet taken the “No Fossil Fuel Money” pledge to swear off donations above $200 from executives or lobbyists, said Evan Weber, co-founder of the Sunrise Movement, a youth-led environmental movement. At least three Democratic presidential candidates — including Washington Gov. Jay Inslee, Sen. Elizabeth Warren (Mass.) and Rep. Tulsi Gabbard (Hawaii) — have taken the pledge.

“We haven’t yet spoken to Julián Castro but are encouraged by his statements and look forward to discussing his support for the Green New Deal,” Weber said.