"Eight years ago at the 2004 Democratic National Convention, then-Senate candidate Barack Obama stepped into the national spotlight and delivered a keynote address that sparked a movement to bring our country together," 2012 Democratic National Convention Chair Antonio Villaraigosa said in an email announcing Castro's selection as the convention's keynote speaker. "On Tuesday, September 4th, Mayor Castro will help President Obama once again deliver a clear vision for our path forward."
In a video accompanying the email, Castro himself said, "I know I've got some big shoes to fill."
So who is the guy who would fill Obama's shoes?
Castro, 37, has served as mayor of San Antonio since 2009. He was born and raised in San Antonio, the son of Rosie Castro, a leader of La Raza Unida, a Mexican-American civil rights group, and a woman The New York Times Magazine described, in a 2010 profile of JuliÃ¡n Castro, as "a well-known '70s firebrand." JuliÃ¡n and his twin brother JoaquÃn Castro -- who serves in the Texas House of Representatives and is running for Congress -- grew up around politics.
"I took him and his brother out to the polls all the time so that they could see me vote," Rosie Castro told NPR in 2010. "They would sometimes come help deliver a sign at one of these houses. In my generation, we were not at the public policy table. You had to insert yourself into the political realities. You had to go to city hall and demand things."
JuliÃ¡n Castro, though, has said he didn't become interested in politics right away.
"When you're 10 years old the last thing you want to do is go to a rally," he said during a TEDx talk in 2009.
During that talk, Castro said it was after he arrived at Stanford University, and saw the level of educational achievement and kind of job opportunities available in the Bay Area, that he started thinking about how San Antonio could reach the same level. The answer, for Castro, was education.
"When I think about the challenges in front of this city, I think about the importance of teachers who can inspire you, the individual difference that they can make in the classroom, the beauty and the strength of a parent who loves his or her child, and is committed enough to stay involved in their education, and make a difference in it," he said. "And the importance of a child who has aspirations -- they see the stars and they want to reach them."
JuliÃ¡n and JoaquÃn Castro passed together through some of the country's finest educational institutions. In San Antonio, they skipped 10th grade together. Together, they went to Stanford University, where, their junior year, they tied for most votes in a student senate election. After Stanford, the brothers went to Harvard Law School, where they both received degrees in 2000. In 2010, JuliÃ¡n Castro told the Times Magazine that he is "a strong supporter of affirmative action because I've seen it work in my own life."
"I scored 1,210 on my SATs, which was lower than the median matriculating student," he said. "But I did fine in college and in law school. So did JoaquÃn."
In 2001, JuliÃ¡n Castro, then 26 years old, was elected to the San Antonio city council. In 2005, he ran for mayor, and was predicted to win in a close race, but ultimately lost to Phil Hardberger, a former judge, by fewer than 4,000 votes.
"I'm 30 years old. I have a long way to go," Castro told The San Antonio Express-News' Jaime Castillo at the time. (Castillo is now Castro's communications director.) "A lot of people have lost and come back."
In 2009, he came back and won. In 2010, Time magazine named Castro to its "40 under 40" list. (Asked were he saw himself "professionally in five years," Castro responded, "mayor of San Antonio.") In February this year, he was named a national campaign co-chair for the Obama campaign.
In his 2010 profile of Castro, Times Magazine reporter Zev Chafets wrote that Castro didn't really speak Spanish:
Early in his administration, Castro assigned his chief of staff, Robbie Greenblum -- a Jewish lawyer from the border town of Laredo whose own Spanish is impeccable -- to discreetly find him a tutor. Rosie Castro's son is now being taught Spanish by a woman named Marta Bronstein. Greenblum met her in shul.
Apparently, Castro's ready to show off the results. At the end of the video announcing his keynote speech, he says: "Thanks, and see you in September. Estamos unidos."