Todd Riffle, spokesman for the New Jersey Republican State Committee, said the state party isn't tied to local Republican clubs.
The Pemberton Republican Club removed the slogan after Democrats alleged racist campaign tactics.
The club's Web master, Ed Kuck, didn't respond to a message left at his home but told The Philadelphia Inquirer that he saw the slogan on an Internet site and copied it onto the club's Web page as a joke.
"I just want to apologize to anybody who was offended, because that wasn't our intention at all," Kuck told the newspaper.
Richard Perr, chairman of the Burlington County Democratic Committee, decried the slogan.
"Comparing Barack Obama to O.J. Simpson, an accused murderer who was found civilly liable for his ex-wife's death, is reprehensible," Perr said. "Moreover, it is a veiled attempt at inserting race into the political arena for which the Republicans should be ashamed."