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Washington CNN —  

Julian Castro labeled the House Republican-led investigation into Hillary Clinton’s emails a “witch hunt” and a “sideshow” from dealing with America’s most pressing problems.

The Housing and Urban Development secretary accused GOP Rep. Trey Gowdy of “very intentionally trying to manipulate this witch hunt to play politics.”

“That’s unfortunate and it’s one of the reasons Congress has a 19% approval rating,” Castro told CNN’s Jim Acosta Sunday on “State of the Union.”

RELATED: First round of Hillary Clinton’s emails released

A trove of Clinton’s emails from her time as secretary of state were released Friday by the State Department. A House panel investigating the attack on the U.S. embassy in Benghazi, Libya, led by Gowdy, has pushed for more State Department emails to be released.

Castro, 40-year-old former San Antonio mayor who emerged on the national scene with a 2012 speech at the Democratic National Committee, was tapped as Obama’s top housing official in 2014. That job, some Democrats have suggested, could be a springboard to a broader role.

Castro dismissed a question about whether he’s the frontrunner to become Clinton’s vice presidential nominee if she emerges as the head of the Democratic ticket.

“If I had a dime for every amount of speculation that happens in D.C., you know, I think all of us would be wealthy,” Castro said. “Who wouldn’t be flattered by that.”

He added that he is focused on issues like veteran homelessness, saying: “The best thing to do in life is do a great job at what’s in front of you.”