A new e-mail making the rounds among Jewish voters in Pennsylvania this week falsely alleged that Mr. Obama “taught members of Acorn to commit voter registration fraud,’’ and equated a vote for Senator Barack Obama with the “tragic mistake” of their Jewish ancestors, who “ignored the warning signs in the 1930’s and 1940’s.”

But where most of the attack e-mails against Mr. Obama have been mostly either anonymous or from people outside of mainstream politics, this one had an unusually official provenance: It was sponsored by the Pennsylvania Republican Party’s “Victory 2008” committee.