Texas Governor Rick Perry's famous "oops" moment during one of his last Republican presidential debates was just one highlight of his often confused campaign across America. It was reportedly made possible by the heavy, deadening influence of prescription painkillers, according to a forthcoming book by two well-sourced reporters.

The claims are made in a forthcoming book by reporters Mike Allen and Evan Thomas, according to excerpts provided to the Republican-leaning Daily Caller website. The book is called "Inside the Circus," and it aims at providing a behind-the-scenes look at the Republican presidential primaries.

The Texas governor's drug use wasn't just the cause of a single humorous, highly embarrassing moment, they add. In another instance, a rival campaign's manager reportedly walked in on Perry while he was urinating... and singing "I've Been Working on the Railroad" at the top of his lungs.

Perry underwent an experimental stem cell procedure on his lower back in 2011, and later admitted that his back issues had caused him problems at the Republican debates. The authors suggest that when he failed to name the three agencies he wanted to shut down, Perry was heavily under the influence just so he could remain standing for two plus hours.

If that's indeed the case, Perry may have some explaining to do, as he previously denied that drugs and alcohol influenced some of his more unusual behavior on the campaign trail, like his speech to a group in New Hampshire that was savagely mocked by The Daily Show.

The governor's strange performance caused a good deal of speculation that he'd been under the influence after video excerpts from that speech went viral on the Internet, but he insisted that wasn't true.

He's since withdrawn from the presidential race and endorsed former House Speaker Newt Gingrich (R-GA).

This video was published to YouTube on Oct. 29, 2012.