Keating is a McCain campaign co-chair.

(CNN) — A prominent surrogate for John McCain on Thursday raised Barack Obama's admitted cocaine use as a teenager and said the Illinois senator should speak candidly about it to the American people.

Speaking to Dennis Miller, a comedian and conservative radio talk show host, former Oklahoma Gov. Frank Keating said Obama should be more forthright about his background and what he called his "very extreme" record.

"He ought to admit, ‘You know, I've got to be honest with you. I was a guy of the street. I was way to the left. I used cocaine. I voted liberally, but I'm back at the center,'" Keating, a co-chair of McCain’s campaign, said Obama should tell voters. "I mean, I understand the big picture of America. But he hasn't done that."

An aide to John McCain said Keating was not directed by the campaign to make the comments.

"We didn’t ask him to do it,” the aide said. “He didn’t clear it with us, but obviously he’s read Senator Obama’s books.”

The Obama campaign has not responded to the comments.

The remarks ring similar to comments made by prominent New Hampshire Democrat Bill Shaheen, a Hillary Clinton supporter, during the primary. Shaheen, who predicted in December that Obama’s drug past would be a major Republican talking point if her were the Democratic nominee. He later apologized for the comments, but stepped down from his role in the Clinton campaign. Black Entertainment Television founder Bob Johnson, another Hillary Clinton backer, also had to apologize after making overt references to Obama's drug use at campaign rally in South Carolina.

In Obama's 1995 book Dreams of My Father, he writes that he was once headed in the direction of a "junkie" and a "pothead. Referring to his emotional struggles as a young man, Obama writes, "Pot had helped, and booze; maybe a little blow when you could afford it. Not smack, though."

Obama did speak during his primary campaign about his past experimentation with drugs and alcohol in high school.

"I made some bad decisions that I've actually written about," he told New Hampshire high school students last November. "There were times when I, you know, got into drinking, experimented with drugs. There was a whole stretch of time where I didn't really apply myself a lot."