While the concept of a national Latino political leader has proven to be elusive over time, Castro's hometown of San Antonio is a place where Latinos have long played a prominent role in politics. A city of 1.3 million, it has grown to become the seventh-largest city in the U.S. It's a major population center for Mexican-Americans, over 60 percent of city residents are Latino, and it was the front line of many civil rights battles in the 1960s and 1970s over matters like bilingual education.
State Rep. Trey Martinez Fischer (D), who represents sections of San Antonio's west side, including Castro's childhood home, says that he and Castro benefited from those fights, but have a slightly different outlook than their predecessors.
"The future of statewide leaders in the state of Texas [is] pro-business Hispanics. But people who also have never forgotten their history when it comes to civil and social justice," he says.
San Antonio's city government structure is such that Castro doesn't have as much power as other big city mayors. A city manager takes care of the day-to-day-management. But Castro has worked to define his own policy agenda. He's positioned himself as pro-business and pro-free trade, but he stresses his biggest priority is education.
His main priority now is a 1/8-cent sales tax increase that would fund full-day public pre-K classes, an initiative targeted to aid the city's low-income families. The measure passed the city council earlier this month and will have to be ratified by city residents in a November ballot initiative to take effect.
"The number one way that we can address these long-term challenges of poverty, of education is to invest in early childhood education. So I'm trying to stretch sometimes the role of a mayor to address those fundamental challenges that we still have as a community," he said.
The measure has positioned him as an ideological analog to Republicans, including Texas Gov. Rick Perry, who enacted major education cuts last year including $200 million from full-day pre-K programs.
He's also been a strong proponent of gay rights. He served as the grand marshal of San Antonio's gay-pride parade in 2009 and worked to approve domestic partner benefits for city employees in same-sex relationships.
While gay rights have become a mainstream position in the national Democratic Party, that hasn't always been the case for the older generation of Latino Democrats, who identify strongly as Roman Catholics and tend to hold more socially conservative views.
But the biggest symbol of his status of a "new generation" of Latino leaders might be the fact he does not speak Spanish. That's not uncommon in San Antonio's Latino community, but it is for a national Latino political leader. His mother says she is the reason he does not know the language; she spoke to him only in English as a child. Castro is trying to learn the Spanish now (he can understand interview questions asked in Spanish and speaks some phrases), and acknowledges it could help his political career if he knew the language better.
"Sí. Es — es importante y es — da beneficio hablar español," he said.
Castro has been on the White House's radar almost since he was first elected mayor in 2009. That year, he attended a economic forum at the White House. As he began to speak, Obama interjected "I thought he was an intern. This guy's a mayor?"