A Democratic senator and potential 2008 presidential candidate said Thursday that White House political adviser Karl Rove (search) must step down if he is linked to the leaking of a CIA operative's name.

Rove faces a fourth grand jury appearance in the investigation of the leaking of CIA officer Valerie Plame's name after her husband, former Ambassador Joseph Wilson (search), criticized the Bush administration's policies in Iraq.

"Even if he's not indicted, if it appears that a top adviser to the president of the United States was trying to harm someone personally for having a different public policy point of view, that's unacceptable behavior in the White House," Sen. Evan Bayh (search) said.

The Indiana senator said Bush's strategists have divided the nation for short-term political gain.

"That kind of cynical strategy has worked well for Karl Rove and the people whose advice he takes, but it's not good for America and it's not the kind of politics I'm going to practice," Bayh said.

Bayh, who is considering a run for the Democratic presidential nomination, visited Iowa to campaign for legislative candidates.