Story highlights CIA Director John Brennan recalled a tough choice when nearing acceptance in the CIA

He decided to admit having voted for a Communist Party presidential candidate

(CNN) At his first polygraph test to enter the CIA, the future director had a secret.

John Brennan on Thursday recalled being asked a standard question for a top security clearance at his early CIA lie detector test: Have you ever worked with or for a group that was dedicated to overthrowing the US?

"I froze," Brennan said during a panel discussion about diversity in the intelligence community at the Congressional Black Caucus Foundation's annual conference. "This was back in 1980, and I thought back to a previous election where I voted, and I voted for the Communist Party candidate,"

Brennan was responding to a question about barriers to recruiting diverse candidates for the intelligence fields, including whether past records of activism could hurt someone applying for a clearance later in life.

The CIA director said the agency's mission is to protect the values of the Constitution -- which include free speech.

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