Republican presidential primary candidate Michele Bachmann is joking that when rival Herman Cain's 9-9-9 tax plan, when turned on its head, represents the Devil.

Bachmann joked that the mirror of 9-9-9 looks like 6-6-6, Satan's number, during Tuesday night's debate. She says "the Devil's in the details" with his economic plan and isn't a viable option.

The Minnesota congresswoman says that Cain's proposal is not a jobs plan, but rather a tax plan.

Cain is a Georgia business executive who has never held elective office. He's has proposed replacing the current tax code with a 9 percent sales tax, a 9 percent corporate tax and a 9 percent income tax.

The candidates made their comments during the Bloomberg-Washington Post Republican presidential primary debate at Dartmouth College.