Mitt Romney's latest ad attacking President Obama features a cameo appearance from Hillary Rodham Clinton slamming the man who's now her boss.

You'll recall that Clinton and Obama engaged in a hard-fought and sometimes bitter Democratic primary battle four years ago. Now, Obama is in the White House, and she's his secretary of State.

The Romney ad is used to fight back at Obama's attacks. It cites a recent Washington Post fact-checking article that says one of the president's commercials charging Romney with being a corporate raider is "misleading, unfair, and untrue."

INTERACTIVE: Candidate Match Game

MORE: Rate campaign ads

"But that's Barack Obama. He also attacked Hillary Clinton with vicious lies," says the ad's narrator.

The Romney ad wraps up with a clip of Clinton from the 2008 campaigning saying, "Shame on you, Barack Obama," in which she is complaining about Obama's attacks on her.

CNN cites a Republican ad-buying source who says Romney is spending $2 million to air the ad in battleground states. The buy is largest in Ohio, and the ad will also air in Colorado, Iowa, North Carolina, New Hampshire, Nevada and Virginia.