UPDATE: SAN ANTONIO — Julián Castro, a former U.S. Cabinet secretary, launched his presidential campaign in the hometown where he served as mayor for three terms surprising few, but jumping to the front of what is expected to be a jam-packed field of White House hopefuls.

Making the announcement at Plaza Guadalupe in the San Antonio's West Side neighborhood where he grew up, Castro said in English and Spanish that he is running for president.

The grandson of an immigrant from Mexico, Castro said his grandmother could have never imagined that two generations later one son would be a member of Congress and another would be standing before the crowd to say, "I am a candidate for the president of the United States of America." He then repeated the phrase in Spanish.

Dozens of other Democrats who hope to challenge President Donald Trump in 2020 will likely follow fast after Castro. That field could include U.S. Rep. Beto O’Rourke of El Paso, Texas, who rose to national fame in a failed bid for the U.S. Senate and is scheduled next month for an interview with Oprah Winfrey.

That could be troublesome, in particular for Castro when it comes to raising money at least in Texas.

But Castro’s first-out-of-the-gate status gives the still-forming Democratic field an early appearance of racial diversity with a candidate whose ancestral roots are in Mexico — the country that Trump, in his 2015 presidential candidacy announcement, said was sending rapists, drug traffickers and criminals to the U.S.

In an interview with NBC News this week, Castro described himself as the “antidote” to Trump.

Castro made the announcement flanked by his wife Erica Lira Castro, his children Carina and Cristian. His mother Rosie, a Chicano activist who took him to political activities as a young boy introduced him as a son of San Antonio, son of Texas, a son of the West Side (of San Antonio) a son of this country.

His identical twin brother U.S. Rep Joaquín Castro also spoke, saying although many of the Democrats who may run are friends, his brother has the best ideas and the biggest heart.

Castro has a lot of work to do to introduce himself to Americans — or reminding them who he is.

Other potential candidates, such as Massachusetts Sen. Elizabeth Warren, who has formed an exploratory committee, Vermont Sen. Bernie Sanders, Sens. Kamala Harris of California and Cory Booker of New Jersey and O’Rourke, have had the benefit of the being in public office and the national spotlight recently.

But Castro's candidacy comes just after the party saw an increased Latino turnout in the 2018 midterms, helping the party to take control of the U.S. House.

"There is a real frustration in our community and desire to show we can’t be bullied,” said Oscar Ramirez, a Democratic strategist. “He has a real opportunity to show that our community has some real power and can’t be pushed around.”

After Obama finished his second term and Clinton lost, Castro left Washington and returned to Texas, where he wrote his memoir “An Unlikely Journey: Waking from my American Dream” and taught university courses in Austin.

He passed on running for Texas governor last year, as did many other Democrats. But Castro kept his hand in the political arena, forming a PAC to contribute to candidates, such as including Stacey Abrams, who lost a bid for Alabama governor and Alexandria Ocasio-Cortez of New York, and potential future backers.

Castro burst on the national scene in 2012 when he delivered the keynote address at the 2012 Democratic National Convention. But Hillary Clinton passed on naming him her running mate in 2016.

Castro was elected San Antonio’s mayor in 2009 and re-elected to two more terms before Obama tapped him to be secretary of HUD, the federal agency that oversees public housing, which Castro lived in during his youth.

At 26, Castro was the youngest person elected to the City Council of San Antonio, the nation’s 7th largest city.

Raised by his grandmother Victoriana and mother, Castro overcame his family’s modest upbringing to attend Stanford and Harvard Law School.

“He’s got an amazing story to tell,” said Democratic consultant Larry Gonzalez, a principal of the Raben Group in Washington. “The Castro family story is the quintessential American story. It is one that will resonate with a lot of Americans who are looking for opportunities that are slipping away. Julian will run a campaign that will address that and resonate with Americans.”

PREVIOUS STORY: SAN ANTONIO — Two days before the expected announcement of his presidential candidacy, Julián Castro described himself in an interview Thursday as "the antidote to Donald Trump."

"Mine is an immigrant story," said Castro, 44, formerly the secretary of Housing and Urban Development in the Obama administration. "It's an American dream story. It's a testament that everybody counts in this country. And I look forward to sharing a vision where everybody, whether you're Latino or any other background, you can reach your dreams in this country.”

Castro, whose grandmother migrated from Mexico in the 1920s, is expected to make the announcement Saturday in San Antonio’s Plaza Guadalupe, surrounded by his twin brother, Rep. Joaquin Castro, D-Texas, his wife, Erica, their two children and his mother, Maria “Rosie” Castro, a political activist.

In an interview at his house here as the president visited the state's southern border with Mexico on Thursday, Castro called Trump's planned border wall "a dumb way to use our resources."

“What we don't need is a wall that stretches the length of the border, some concrete wall that people are just going to be able to go over or go under,” he said.

A former mayor of San Antonio, a city in which Hispanics represent a majority, Castro made his case by emphasizing his roots and experience in comparison to the 20 or so other candidates expected to throw their hats into the ring -- and particularly Beto O'Rourke, another young Texan making headlines.

"I don't think it's necessarily about always having the shiniest words or approach, "Castro said. "People want to know that somebody has the right experience and that they have the right vision to make sure that their family can succeed in this country. And I have that.”

In 2012, after Castro gave the keynote speech at the Democratic National Convention, some called him the future of the party. But he has since been eclipsed by other Democratic stars.

“Well, I'm not the frontrunner,“ he jokingly acknowledged. “But, you know, I don't think I can think of one time in my life where I was the frontrunner. If you go to the neighborhood that I grew up in, nobody that was growing up there was the frontrunner. And today, in this country, there are a lot of people that don't feel like the frontrunner. … Fundamentally, this campaign is not going to be about me.”

When asked what his future candidacy represented for Hispanic Americans, Castro said, “I'm proud to be Latino, I'm proud to be American. And as president, I would have to represent all Americans.

"At the same time, there's no question that today, a lot in the Latino community fell targeted by this president,” he said, referring to Trump's hardline immigration stance and anti-immigration rhetoric.