Actually, the "attacks" on Cleland that democrats tend to cite were made as part of the 2002 campaign and predate his 2003 and 2004 actions in support of Kerry's presidential bid.

They involved questions about Cleland's national security views:
  • a tough anti-Cleland ad [was] broadcast featuring Osama bin Laden and Saddam Hussein. The ad didn't morph Cleland into either of these figures or say that he supported them. It noted at its beginning that the United States faced threats to its security as the screen was briefly divided into four squares, with bin Laden and Saddam in two of them and the other two filled with images of the American military.

    It went on to explain that Cleland had voted 11 times against a homeland-security bill that would have given President Bush the freedom from union strictures that he wanted in order to set up the new department. The bill was co-sponsored by his Georgia colleague Sen. Zell Miller, a fellow Democrat. Bush discussed details of the bill personally with Cleland, and Chambliss wrote him a letter prior to running his ad urging him to support the Bush version. Cleland still opposed it, setting himself up for the charge that he was voting with liberals and the public-employees unions against Bush and Georgia common sense.

    If you can't criticize the Senate votes of a senator in a Senate race, what can you criticize?


So it wasn't even a question of "attacking" Cleland for his support of Kerry. It was a question of people exercising their constitutionally protected right to criticize the voting record of an elected official.