The group, the Republican Jewish Coalition, plans to begin a multimillion-dollar advertising campaign in the coming weeks called “My Buyer’s Remorse,” targeting voters in Florida, Ohio and Pennsylvania, aides said. The campaign uses testimonials from people who say they regret supporting Mr. Obama because of his economic policies and his posture toward Israel, in hopes of cutting into the wide advantage Democrats have held over Republicans among Jewish voters…

The fight for the Jewish vote is more of a hunt-and-peck search for disgruntled voters, considering that Mr. Obama won more than 70 percent of votes among Jews in 2008, according to exit polls. But with an estimated 600,000 Jewish voters in Florida, a critical swing state, Democratic leaders said they were not taking the constituency for granted, and they acknowledged a need to increase enthusiasm among Jews before November.

“They figure if they shave off a few points here and a few points there in the Jewish population through lying and distortions, they can win,” said Representative Debbie Wasserman Schultz of Florida, chairwoman of the Democratic National Committee. “But they can’t dress themselves up to be something appealing to the Jewish community when they aren’t.”