Updated at 2:15 p.m: Updated to

include interview with Julián

Castro.

SAN ANTONIO — Julián Castro, courting progressives in hopes he can overtake a large field of Democrats, announced Saturday morning in his hometown that he's running for president.

Castro promised that if elected he would push for Medicare for all, universal prekindergarten instruction, changes to the cash-bail system and an end to police violence against African-Americans.

Calling climate change a mortal threat to humanity, Castro said his first presidential action would be to issue an executive order recommitting the U.S. to the Paris climate accord, a multinational effort to reduce greenhouse gas emissions.

"We're going to say no to subsidizing big oil and say yes to passing a Green New Deal," he said, referring to an economic stimulus program that's modeled on former President Franklin D. Roosevelt's New Deal. It would tackle environmental degradation and income inequality.

"We can fight climate change and create great jobs here in America," Castro told more than 1,000 supporters in his old West Side neighborhood.

"Together we will show that hope can be bigger than fear, that light can be bigger than darkness, and that truth can be bigger than lies." #Julian2020 — Julián Castro (@JulianCastro) January 12, 2019

Castro, a former San Antonio mayor and Obama administration Cabinet member, saved perhaps his fiercest rhetoric for a rebuke of President Donald Trump's immigration policies.

"Yes, we must have border security," he said. "But there is a smart and humane way to do it. And there is no way in hell that caging children is keeping us safe. We say no to building a wall and say yes to building community."

Without mentioning the shutdown of the federal government, now the longest ever, Castro denounced Trump's motivation for it. He scoffed at Trump's visit to McAllen last week, an effort to show that a bigger, longer barrier is needed on the U.S.-Mexico border to avert what the GOP president calls a humanitarian and national security crisis.

"Well, there is a crisis today — it's a crisis of leadership," Castro said. "Donald Trump has failed to uphold the values of our great nation."

Castro also pledged to uphold abortion rights, fight discrimination against gays, raise the minimum wage and "protect the right of workers to organize in an economy that is quickly changing and leaving too many families behind."

As have some of the Democratic Party's most liberal presidential contenders, such as Massachusetts Sen. Elizabeth Warren, Castro has endorsed free community college — though he didn't expressly say that Saturday.

"We'll work to make the first two years of college, a certification program or an apprenticeship accessible and affordable," he said, so more young adults can "get a good job without drowning in debt."

Castro, former President Barack Obama's secretary of housing and urban development during Obama's second term, spoke of soaring housing costs as a crisis.

"Families are doubling up, sleeping on the couches of relatives or even on the streets," he said. "We will invest in housing that's affordable to the middle class and to the poor."

1 / 5Julian Castro, former HUD secretary and San Antonio mayor, announced his candidacy for president at Plaza Guadalupe on Jan. 12, 2019, in San Antonio. If successful, Castro would be the first Hispanic candidate to win the White House.(Edward A. Ornelas / Getty Images) 2 / 5SAN ANTONIO, TX - JANUARY 12: Julian Castro, former U.S. Department of Housing and Urban Development (HUD) Secretary and San Antonio Mayor, with his wife Erica Lira Castro greets supporters before announcing his candidacy for president in 2020, at Plaza Guadalupe on January 12, 2019 in San Antonio, Texas. If successful, Castro would be the first Hispanic candidate to win the White House. (Photo by Edward A. Ornelas/Getty Images)(Edward A. Ornelas / Getty Images) 3 / 5Suppporters hold up signs as former United States Secretary of Housing and Urban Development JuliÃ n Castro announces his candidacy for president of the United States in his hometown of San Antonio, Texas on January 12, 2019. (Photo by SUZANNE CORDEIRO / AFP)SUZANNE CORDEIRO/AFP/Getty Images(SUZANNE CORDEIRO / Getty Images) 4 / 5A young boy peeks under a banner as he watches former San Antonio Mayor and Housing and Urban Development Secretary Julian Castro make his announcement to seek the 2020 Democratic presidential nomination, Saturday, Jan. 12, 2019, in San Antonio. (AP Photo/Eric Gay)(Eric Gay / AP) 5 / 5Former United States Secretary of Housing and Urban Development JuliÃ n Castro announces his candidacy for President of the United States in his hometown of San Antonio, Texas on January 12, 2019. (Photo by SUZANNE CORDEIRO / AFP)SUZANNE CORDEIRO/AFP/Getty Images(SUZANNE CORDEIRO / Getty Images)

Crowded field

If successful, Castro, 44, would be the first Hispanic and one of the youngest presidents ever elected.

Castro appeared at Plaza Guadalupe after being introduced by his mother, Rosie Castro, a '70s leader of La Raza Unida, the radical Texas movement that pushed a strong "Chicano" identity and promoted civil rights for Mexican-Americans. Rosie Castro called her son "a son of San Antonio," "a son of Texas" and "a son of the United States."

"I'm running for president because it's time for new leadership. It's time for new energy," he said, in English and Spanish, adding that he wants the U.S. to be the most prosperous, smartest and healthiest nation on earth.

Earlier in his speech, he addressed his upbringing on San Antonio's West Side.

"Look around, there are no front-runners born here but I've always believed that with big dreams and hard work, anything is possible," he said.

Castro's twin brother, Rep. Joaquin Castro, will serve as the campaign chairman. Maya Rupert will be campaign manager.

Nearly a decade ago, Julián Castro was considered a budding star. He gave the keynote address at Obama's second nominating convention. He was mentioned as a potential running mate for Hillary Clinton in 2016.

But his unwillingness to follow up his service as HUD secretary with a bid for statewide office in Texas, such as governor or U.S. senator, has brought him criticism for being too cautious.

Vacuum filler? Beto O'Rourke

While the 2020 Democratic presidential field is likely to be crowded, Castro's biggest hurdle may be at home in Texas, where there are signs that former U.S. Rep. Beto O'Rourke, now the most popular Democrat in Texas, is seriously considering a presidential campaign.

Texas Republican Chairman James Dickey of Austin, who held a conference call with reporters to denounce Castro as a leftist and a failed mayor, said he agrees Castro felt a need to jump into the race now because he's been eclipsed by O'Rourke in Texas.

"He's got to be incredibly miffed at how quickly and how easily the void of his absence was filled in," Dickey said.

As O'Rourke did in his failed Senate run against Ted Cruz, Castro has said he won't take money from political action committees.

"So you know that this is always — and only — about you, I won't be accepting a dime of PAC money in this campaign. And as president, we will work to overturn Citizens United, to get big money out of politics," he said, referring to a 2010 Supreme Court decision that the First Amendment protects corporations' and unions' rights to spend money to persuade voters in elections.

Joaquin Castro, asked if Julián Castro is sweating an O'Rourke candidacy, insisted his brother is focusing on his own race and not whether the former El Paso congressman would be a rival for the nomination.

"He's just going to go and do the hard work of focusing on his vision and getting the message out to people," Joaquin Castro said. "We understand it's a competition and a race, but you really can't focus on what other folks are doing."

When asked where Texas donors waiting for the entire field to take shape should place their money, he said: "I would ask them to follow their heart and their mind."

Julián Castro said after the rally that its size and composition encouraged him. People in New York and Washington, D.C., are underestimating his support, he told The Dallas Morning News.

Many attendees were "working class," he said. Castro rode public transit — Bus No. 68 — to the event. The crowd interrupted him repeatedly with chants of "Julián! Julián!"

.@JulianCastro and @JoaquinCastrotx on the bus in San Antonio on the way to Castro’s announcement for president at Plaza Guadalupe near where they grew up feels like something new. https://t.co/eFZZzBrqtP pic.twitter.com/tyefNGDOS7 — Adrian Carrasquillo (@Carrasquillo) January 12, 2019

'Bigger than lies'

Bardo Perez walked around in the crowd carrying a framed photo of his father, Estanislao Perez, standing with famed organizer Cesar Chavez.

The younger Perez said Castro's candidacy links the past with the present, particularly since Rosie Castro was a Chicana activist.

"Julian has strong values and he will make us proud," Perez said.

Abby Train, an economics professor at Texas State University, said Castro was a good mayor and would bring his understanding of economic policy to the White House. Castro is a marked contrast to Trump, Train said.

"He's a decent human being and that's what we need more than anything else," she said.

Castro called for unity among Americans.

"We will show that hope can be bigger than fear, that light can be bigger than darkness, and that truth can be bigger than lies," he said.

He announced plans to travel to Puerto Rico on Sunday and Monday and to New Hampshire on Tuesday and Wednesday for campaign events. He'll meet privately with Democratic Texas state lawmakers in Austin on Tuesday morning.