There are any number of reasons why Newt Gingrich shouldn’t be entrusted with the presidency. I’ve knocked him around from the left. Jennifer Rubin continually uses her “Right Turn” blog to give the former speaker a right hook. But this morning, Herman Cain gave yet another reason why the former speaker should not be president — and why he himself should never get his own hard pass to enter the White House unescorted.

Trying to explain why his endorsement of Gingrich, on top of his quizzical endorsement of “the people” earlier this month, was “not exclusive of each other,” Cain had this to say to Fox News anchor Bill Hemmer in the opening minute of an interview this morning.

He has embraced the idea of replacing the tax codes, and one of the major considerations now in his mind is my 9-9-9 plan, which was a very important issue for me, as you know. He hasn’t said that he’s definitely going to do it, but he’s giving it serious consideration, and he has shown that by asking me to be co-chair of his economic growth and jobs plan.

It has been firmly established that Cain’s “9-9-9” plan makes no sense. An analysis by The Tax Policy Center, for instance, found that it would raise taxes on 84 percent of households. He couldn’t even explain (convincingly or otherwise) during a crucial interview last year on “Meet the Press”why the poor would pay more under “9-9-9.” That Cain says Gingrich is giving the plan “serious consideration” can only be explained as desperation. That Cain says Gingrich has made him the co-chair of an economic growth and jobs plan is the very definition of madness.