By Alina Selyukh and Harriet McLeod
WASHINGTON/CHARLESTON, South Carolina (Reuters) - Late-night TV comedian Stephen Colbert is urging his South Carolina fans to cast votes in Saturday's Republican presidential primary for former candidate Herman Cain, a way Colbert says he will gauge support for his own mock presidential campaign.
Who is not laughing? South Carolina Democrats.
The state's open primary allows Democrats and independents to vote in the Republican primary, and Colbert earlier this week called on his home state supporters to cast votes for Cain. The former pizza executive suspended his campaign in December amid allegations of sexual harassment and infidelity but remains on the ballot.
"They're keeping me off the ballot on the technicality that I'm two-and-a-half months late to file. Fine, split hairs," Colbert said on his "The Colbert Report" TV show on Comedy Central.
The unamused state Democratic Party shot back with an email titled "NO to GOP Primary": "The South Carolina Democratic Party... DOES NOT encourage people to vote in the Republican Presidential Primary."
The pro-Colbert Super PAC, Americans for a Better Tomorrow, Tomorrow, has already spent $65,600 on advertising in South Carolina. Political action committees (PACs) are groups with great clout in U.S. politics that are legally separate from candidates.
A statewide poll by the nonpartisan Justice at Stake Campaign found 7 percent of Republican-leaning voters saying they would definitely vote for Colbert in Saturday's primary if his name were on the ballot.
After Colbert called on all to take part in the open primary, his "exploratory" campaign mobilized with Internet outreach and the Super PAC launched a new ad to drum up support for Cain.
The Democrats' concerns are no laughing matter. Voting for Colbert via Cain would stir up the voter files, likely landing Democrats' contacts in Republican fundraising and mailing databases.
Besides, Democrats also are hoping South Carolinians turn out to vote for President Barack Obama in their own January 28 primary. Double-dipping in the two primaries is not allowed.
The local Republican Party, on the other hand, appears happy to play along.
"I'm enjoying watching it all," South Carolina Republican Party Chairman Chad Connelly told Reuters. "I like Stephen, he's a potential donor. ... We'd love to have a huge voter turnout."
Connelly said the party is not making special preparations in expectation of extra voters and was skeptical about translating the tally of Cain votes, which will be counted and reported, into Colbert's success.
"I'm not sure how Stephen is going to separate out the people who vote for Cain because he said so and people who vote because they like Cain," Connelly said.
Cain, for his part, is in the on the joke, scheduled to appear alongside Colbert at his rally "in support of their non-candidacies" in Charleston on Friday.
"Together, these two unique voices will declare that they are the same man," read the press release for the event.
Cain's campaign could not be immediately reached for comment, but the candidate tweeted he would make an "unconventional endorsement" at the Southern Republican Leadership Conference later on Thursday.
(Editing by Will Dunham)