Herman Cain’s presidential campaign is desperately trying to get back on message and regain the momentum it was experiencing before allegations of sexual harassment turned the nation’s attention from his 9-9-9 tax plan to questions about his character. But after an interview with the editorial board of the Milwaukee Journal Sentinel on Monday, political observers are once again questioning Cain’s fitness to be president. The reason has nothing to do with what some have described as a cavalier attitude toward women and centers on what appears to be a glaring lack of foreign policy knowledge.

During the interview, which was videotaped and has now gone viral, Cain struggled, physically and mentally, to respond to a question about whether he agreed with President Obama’s response to the uprising in Libya. The moment was reminiscent of Texas Gov. Rick Perry’s “Oops” moment in last week’s presidential debate when he struggled to remember the name of one of the three federal agencies he’d eliminate if elected.

“Okay, Libya,” Cain said, leaning back in his chair and looking up to the ceiling.

He then sought to confirm that Obama had supported the uprising and called for the removal of Moammar Gadhafi to ensure that he and his interviewers were on the same page before providing a response. A squirming Cain started to explain why he didn’t agree with Obama’s handling of Libya but got flummoxed because he had “all this stuff twirling around in my head” and in the end never actually answered the question.

His brain freeze reinforced speculation among many analysts that Cain is not “ready for prime time,” said Michael Tanner, a senior fellow at the Cato Institute, and could perhaps do even more damage to his White House bid than the sexual harassment claims. The supporters who rallied around Cain and accused the media of engaging in a “high tech lynching” won’t be able to make the same charges in this situation, Tanner added.

Cain’s spokesman tried to brush off the matter by saying the candidate had gotten just four hours of sleep before the interview, which made it difficult for him to “switch gears between so many different topics.” But as Tanner noted, presidents don’t always get eight hours of sleep at night.

Tanner also predicts that while down, Cain’s definitely not out. That is in large part due to the ongoing support of conservatives who still struggle to support Mitt Romney, the likely inevitable nominee, whom they feel they cannot trust.

“That’s what has sustained Cain. People thought that what he said is what he believed,” said Tanner. “That counts for a lot, but in the end it s not enough.”

(Photo: Chip Somodevilla/Getty Images)