Having a hip celeb on the stump stage could actually backfire for candidates looking to up their cool factor.
"Often, what ends up happening is the candidate ends up looking more awkward with the celebrity next to them," Jackson said. "It draws an even sharper image of the candidates' stiffness or whatever with the celebrity being there."
To Romney's credit, his stage-sharing with Kid Rock on Monday might have been awkward because the rock star never actually endorsed him, but Romney managed not come off stiffer than unusual next to the laid-back rocker, Jackson said.
"He played off the fact that he's not cool, that he's a problem solver," Jackson said. "People sometimes like geeks and he's got to play to the strengths he's going for."
Romney's lack of passionate celebrity endorsers is not entirely surprising because most of Hollywood's big hitters tend to skew Democratic. But even President Obama is finding some unconvinced endorsers among his 2008 club of supportive superstars.
Matt Damon spoke at rallies, attended fundraisers and appeared in videos supporting Obama's 2008 campaign, but has publically criticized the president this election cycle.
"You know, a one-term president with some balls who actually got stuff done would have been, in the long run of the country, much better," Damon told Elle Magazine in December. "People are literally without any focus or leadership, just wandering out into the streets to yell right now because they are so pissed off."
But will Damon switch his support to a Republican challenger?
"Good God, no!," he told the Independent in March.
Obama is already hitting Hollywood Boulevard to try and win back the support of the deep-pocketed, highly enthusiastic California crowd. He took a three-day fundraising swing through the West Coast earlier this month, schmoozing with the likes of Jack Black and Will Ferrell.
"He has to work to rebuild the enthusiasm he had in '08," Jackson said. "And I don't doubt one bit that the celebrity endorsements and the deployment of that celebrity army out in the field will help."
Jackson said that in a close election, that star power "could make a difference," especially because those big names tend to draw out young voters.
"Romney just isn't going to have that," Jackson said. "He's not going to have that enthusiasm from the youth."