Last night’s debate in New Hampshire was supposed to be about Mitt Romney. It was instead about Herman Cain’s “9-9-9” plan, which the former pizza company executive claims will revitalize the economy, end partisan bickering in Washington, balance the budget, and generally lead to an American utopia.

Ideally, we could do what the political world has done for months: generally ignore this foolish gimmick. But when a policy idea — I use the phrase loosely — becomes the central focus of a debate for presidential candidates, it’s probably worth taking the time to look at it in a little more detail.

What Cain calls his “9-9-9” economic plan is basically his approach to tax policy — he envisions a system with a 9% income tax, a 9% corporate tax, and a 9% sales tax. Chris Cillizza praised it this morning for its “beautiful, political simplicity.”

The bad news is, political simplicity notwithstanding, the plan doesn’t make any sense. Bruce Bartlett, a Republican economist and veteran of the Reagan and H.W. Bush administrations, published an analysis of the plan yesterday, explaining that it would, as a practical matter, raise taxes on the poor considerably, make it more expensive for businesses to hire workers, and increase the deficit.

At a minimum, the Cain plan is a distributional monstrosity. The poor would pay more while the rich would have their taxes cut, with no guarantee that economic growth will increase and good reason to believe that the budget deficit will increase.

Even allowing for the poorly thought through promises routinely made on the campaign trail, Mr. Cain’s tax plan stands out as exceptionally ill conceived.

Michael Linden, the Center for American Progress’ director of tax and budget policy, ran the numbers on Cain’s plan and came to the same conclusion.

And while we’re at it, the “9-9-9” proposal, at least in its current form, also suffers from constitutional problems.

Wait, it gets better. Last night, Cain said he relied on “well-recognized economists that helped me to develop this 9-9-9 plan,” but he won’t tell us who they are. He said the plan has been “well studied,” but he won’t say by whom or what they found, specifically. Cain added that his campaign had an “independent firm … dynamically score” his plan, but he won’t share the results of the analysis.

This isn’t a policy; it’s a joke.

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Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.