(CNN) John Hickenlooper, the former Democratic governor of Colorado who is running for president, went into great detail on Wednesday evening explaining the time he took his mother to see an X-rated movie at a theater in the 1970s.

The awkward moment started with a question from CNN's Dana Bash during a town hall in Atlanta. She brought up his memoir, in which he talked about seeing a pornographic movie with his mother. Bash then let him have the floor.

The movie, Hickenlooper said, was "Deep Throat" -- the X-rated film that turned into a pop culture phenomenon after its release in 1972.

Hickenlooper said he had left for college and had returned home to visit his mother for Thanksgiving. His father had died when he was 8, and when Hickenlooper left home for college, it was the first time his mother had been alone in years, he said. The gravity of that hit him when he came home for the holiday that year.

"I promised, I called a friend in Philadelphia -- and ... we didn't know what an X-movie was. We thought it was a little naughty, but we didn't think it was that bad," Hickenlooper said. "You've gotta understand, I was 18 years old."

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