“San Antonio is one of the most livable cities

in the nation.”

… with a twin brother, who is also in politics.

“I'm one minute older.”

Colbert: “One minute older?”

“He routinely goes around telling people

that the way to tell us apart is that

I'm a minute uglier than he is.”

And he found his footing on the debate stage,

but is still lagging in the polls.

“We need a Marshall Plan for Honduras

and Guatemala and El Salvador,

so that people can find

safety and opportunity at home.”

Julián Castro is running for president.

So who is he?

Castro was born and raised in San Antonio,

the grandson of a Mexican immigrant.

“She ended up working her entire life

as a maid, a cook and a babysitter

so that my mother could have a better shot in life.”

After attending Stanford and Harvard Law,

Castro came back to San Antonio

and was elected to the City Council when he was 26.

He ran for mayor in 2005 and lost.

Four years later, he tried again and won.

“I thought he was an intern.

This guy's a mayor?”

“San Antonio, Texas.”

“I'm messing with you, I know who you are.”

One of his priorities as mayor

was implementing a full-day pre-K program.

“If you have a dollar to spend in education,

that dollar is best spent early on with young people

before they ever get behind in the first place.”

In 2012, he was in the national spotlight

as the first Latino keynote speaker at the D.N.C.

“Ours is a nation like no other.

A place where great journeys can

be made in a single generation, no matter who

you are, or where you come from.”

President Obama tapped Castro to be his housing secretary,

and now he's seeking to return to D.C.

So what is his platform?

“We stand up for immigrants.”

Castro's made immigration his cornerstone.

He was the first candidate to propose

repealing the section of immigration law

that criminalizes illegal border crossing.

“Some of us on this stage have called to end that section,

to terminate it.

Some, like Congressman O'Rourke, have not

and I want to challenge all of the candidates to do that.”

And he supports higher minimum wage,

rejoining the Paris Climate Accords,

gun control and reforming the policing system.

So what are his chances?

It took a while for Castro to have a breakout moment.

“You know, I wasn't born a front-runner.

I didn't grow up a front-runner.”

But then came the debates.

And that's when Castro started gaining momentum.

“What we need are politicians that actually

have some guts on this issue.”

Moderator: “Thank you, Secretary.

Mr. Vice President, please, your response.”

But is his debate performance enough?

Despite pushing the party on immigration,

Castro continues to struggle in the polls

and in fund-raising,

keeping him near the bottom of the pack.