The ebook suggests that Perry was under the influence of painkillers during portions of the primary, particularly during at least one debate in October. The book quotes a rival campaign manager recounting Perry behaving oddly in a bathroom ahead of the debate by standing too close and "merrily" singing "I've been working on the railroad." 

His lackluster debate performances — including one incident in which he struggled to finish an answer about the Cabinet-level government agencies he proposed to eliminate — have often been cited as one reason his campaign soured early. He had given "fatigue" as a reason for his poor performance, and in December admitted that back pain might have hindered him as well.

“You have a fusion on your back and it takes you a while to get back on your game,” Perry told Iowa Public Television. At that time, he referred to physical and mental improvement over the past few months. “I was pretty fatigued. But no excuses, it was there, it's what it is and, look, if anybody's looking for a perfect candidate I'm not it.”

Sullivan said the back surgery influenced Perry's health, but did not play a role in the campaign.

"The governor has stated that July back surgery prevented his regular exercise routine and Perry officials have also repeatedly and truthfully denied that pain medicine was a factor in the campaign," he said. "Politico's claims are false, unsubstantiated and ultimately harmful to the political and electoral process, and to the trust in the media that covers the process."

Perry dropped his bid for the White House in January.