PHILADELPHIA — Rep. Joaquin Castro has been making the usual rounds — Texas delegation breakfasts and Latino unity events — at this year's Democratic National Convention.
But instead of being asked about his brother's chance of becoming Hillary Clinton's vice presidential nominee, the focus has shifted to his own political future.
He's thrust himself into the 2018 Texas U.S. Senate race discussion, taking shots at Sen. Ted Cruz. (Cruz "freaked out" when he heard Castro was ready to take him on, according to Castro.)
With Julián Castro sidelined because of a decision in recent weeks by the Obama administration to bar cabinet officials from addressing the convention, the responsibility falls on Joaquin Castro to speak for the most high-profile Mexican-American family in Democratic politics.
In his speech, obtained by BuzzFeed News, Castro will tell the story of his grandmother, who came from Mexico to the United States in 1922. "She wasn't a rapist or a murderer," Castro will say, "she was a six-year-old orphan."
Like his brother, Castro will recall what his family went through seeing signs that said "No Dogs or Mexicans Allowed," but appeal to a vision of America that allowed them both to succeed.
"The hero of that story is never the one who sides with hate," Castro will say, according to the prepared remarks. "The hero of that story will never be Donald Trump."
He will also seek to contrast what he calls attempts by Trump to make politics a zero sum game.
Regarding national security, "We can keep America safe and still welcome the next generation of immigrants without a religious litmus test," he will say. On justice, "We can back our brave men and women in blue and still believe that Black Lives Matter."
While Castro would be an underdog in a matchup with Cruz, it would pit two starkly different high-profile Hispanic politicians against each other. The Mexican-American Castro's mother was a civil rights activist in the Chicano movement, while Cruz's family left Cuba and have railed against the dangers of communism, embracing staunchly conservative positions.
For Julián Castro, who was vetted but was not chosen as Clinton's vice presidential pick, the talk has now turned to his political future as well. He popped a short-lived trial balloon this week after Democrats as well as the U.S. Hispanic Chamber of Commerce president Javier Palomarez floated the idea of him taking over as the permanent DNC chair in the wake of Debbie Wasserman Schultz's resignation.
"I have no interest in that," Julian Castro told BuzzFeed News after his speech at a Latino Leaders Network luncheon. "I think Donna Brazile is going to do a fantastic job between now and November and after that we'll see what happens but I have no interest in that."