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.

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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.