Herman Cain owes much of his rise to the head of the Republican presidential field to his catchy 9-9-9 tax plan. Even though an analysis by the nonpartisan Tax Policy Center found that the nine-percent flat tax plan would raise taxes on the poor and cut them for the rich, it sounds catchy and Cain’s supporters have embraced it.

But when the White House hopeful tried to tout 9-9-9 during an appearance on the Late Show With David Letterman that will be broadcast Friday night, his sales pitch fell flat with the host. When Letterman, who can be a tad crotchety when the mood strikes, told him that he doesn’t understand what the plan means, Cain attempted to deliver his standard description of it as a “bold economic growth plan” but was interrupted.

“I know it’s bold,” Letterman said. “But you don’t even know what it means. I heard someone say to you, ‘How would so and so and so and so be handled under 9-9-9?’ And you said: I don’t know!”

Cain’s defense was that it was an “obscure” question.

Letterman told Cain that dealing with obscurity is something that presidents must deal with and offered up his own 9-9-9 plan to the former pizza executive.

“I mean, I like it, it’s clever, 9-9-9, it’s fun.… And you ought to get some sort of toll-free number, Herman Cain, you dial 9-9-9, you get a free pizza,” Letterman said. “Come on, what are we talking about?”

"Instead of a free pizza when you dial 9-9-9 you're going to be able to get a job, that's the whole point, OK?" Cain said. "I'm about creating jobs."

When Letterman suggested that the economy may be "beyond solvability at this point," Cain quipped, "Are you trying to talk me out of this? He's trying real hard to talk me out of this."

(Photo: CBS/John P. Filo/Landov)