Comedy Central/ABC News

Comedian Stephen Colbert's not-yet-announced, still just exploratory, possible presidential campaign has hit a major speed bump: Colbert is not on the South Carolina primary ballot and the state does not allow write-in candidates.

So instead of urging Republicans to pick Colbert in Saturday's primary, the pro-Colbert Super PAC "Americans for a Better Tomorrow, Tomorrow"   released an ad Monday night telling supports to vote for former presidential candidate Herman Cain, whose name still appears on the South Carolina ballot.

"There is one name on the ballot that stands for true Americannimity: Herman Cain," the ad's narrator says. "Americans for a Better Tomorrow, Tomorrow believes a vote for Herman Cain is a vote for America."

But as the narrator asks viewers to cast their vote for Cain, images of Colbert standing proudly before an American flag fill the screen and a red arrow pops up next to his head that says "Seriously, This guy."

"Because Herman Cain and I are so similar, I think that if this Saturday Herman Cain were to get a significant number of votes that would be a sign that voters are hungry, hungry for a Stephen Colbert campaign," Colbert said on his Comedy Central show Monday night. "Anybody who shares my values can show it by voting for Herman Cain."

The last 15 seconds of the 1-minute ad shows a close-up of Colbert with a slow smile spreading across his face, an obvious spoof of Cain's now-viral campaign ad which also ends with five seconds of Cain slowly smiling.

"Tell the world how much you love Herman Cain," Colbert said on Monday's Colbert Report. "Because folks if our message is going to be taken seriously we are going to have to do more than just raise money and raise awareness, we're going to have to raise Cain."

Cain, who suspended his campaign in early December when faced with accusations of sexual harassment, is one of nine names on the South Carolina ballot. The deadline to get on the ballot passed more than two months ago.   Besides the five announced candidates, former GOP hopefuls Jon Huntsman and Michele Bachmann and Libertarian Gary Johnson are also on the ballot.

This is the second campaign ad that the pro-Colbert Super PAC, now run by his fellow comedian Jon Stewart, has released this week as part of a $7,600 ad buy that is airing on Charleston's CBS station. The latest ad began airing this morning, said the station, WCSC,General Manager Rita Scott.

Scott said two additional ads will be released this week, one about Newt Gingrich, which will air twice on Wednesday, and one solely about Colbert, which airs twice on Thursday.

The first ad, which hit South Carolina airwaves on Sunday, accuses Mitt Romney of being a "serial killer," calling him "Mitt the Ripper."

Colbert said Monday that the ad was the "most shocking attack ad yet" from the "shadowy outside group," which, he emphasized, he cannot legally coordinate with.

"So is Mitt Romney a serial killer? I don't know, but that question is out there now," Colbert said, adding that "once again I need to make it as clear as the bleach Mitt Romney may or may not use to dissolve the bones of his victims, this commercial is the sole responsibility of the person I turned my PAC over to four days ago."

Colbert's joke-laden commentary on Super PACs may make entertaining late-night television, but it also brings up a point Colbert has made central to his possible presidential bid. This is the first election where independent groups can collect and spend unlimited amounts of money to support political candidates without having to disclose their donors and which candidates have no authority over.

PACs have spent upwards of $7 million to run ads in South Carolina, more than double the amount candidates themselves have spent. The majority of those ad dollars have been spent by a pro-Gingrich Super PAC to attack Romney's business background and by a pro-Romney Super PAC to attack Gingrich's abortion stance.