In June 2011 , Castro announced that he was running for a seat in the United States House of Representatives in the newly-drawn . He was initially set to challenge fellow Democrat and nine-term incumbent Lloyd Doggett , whose home in Austin had been drawn into the district , in the Democratic primary However , on November 28 , after Charlie Gonzalez of the neighboring 20th District announced his retirement after seven terms , Castro announced his intent to run instead for the 20th District seat . He was unopposed in the Democratic primary , all but assuring him of being the next congressman from this heavily Democratic , Hispanic-majority district . At the 2012 Democratic National Convention , he introduced his brother Julián as keynote speaker . In November 2012 , Castro defeated Republican David Rosa 64 % -34 % . becoming only the fifth person to represent this district since its creation in 1935
2012 Democratic National Convention
2012 Democratic National Convention
Joaquin Castro