Herman Cain’s 9-9-9 economic plan got lots of attention at last night’s debate. It was said, in fact, 24 times, by NBC’s count.

Despite Jon Huntsman’s quip, it is not the “price of a pizza.”

So what is it, and what does it do? It would completely change the tax structure in the country and replace it with a:

- 9% income tax,
- 9% national sales tax, and
- 9% corporate income tax

Deductions, including the popular mortgage deduction, would be eliminated. There would be an exception, however, for charities.

It eliminates the capital-gains tax, which benefits those who make money in the stock market. And it eliminates the payroll tax, which funds Social Security.

Because of the current progressive tax system, the poor, working class, and many considered middle class pay zero (or close to zero) in income tax. They account for about 40% of the country.

The non-partisan Tax Policy Center is readying a report on Cain’s plan, though it is waiting for more details from the campaign. But it has come to some conclusions already.

Cain’s plan "cuts taxes for the rich and raises taxes on the poor,” Roberton Williams, a senior fellow at the center, tells First Read. He added that it would create a "much more regressive tax system.”

The plan would represent a “major tax cut” for the rich and raise taxes “substantially” on the poor and middle class, Williams said. "Given that a big chunk doesn’t pay any income tax, this would be a big tax increase on people at bottom end. At the top end, the opposite happens."

The top end would go from about a 35% income tax rate to 9%. "That's a big, big drop," Williams said, adding that the capital-gains tax would be another added benefit for the wealthiest. "People at the top would see far and away the largest share of the gains. Those people are going to see a huge tax cut."

Currently, there is no federal sales tax. There are state sales taxes, however, and Cain’s plan would add 9% to those. So, in Iowa, for example, where there is a 6% sales tax, that would mean a 15% sales tax.

On MSNBC’s The Daily Rundown with Chuck Todd this morning, Cain defended his plan, saying there has been a lot of “misinformation” and “misperceptions” about it. He noted that with the payroll tax being eliminated, that would be something of a built-in cushion to deal with the sales tax.

He also said a family of four with a household income of $50,000 a year would pay $10,000 in income taxes and have enough left over to pay for goods, despite the sales tax increase.

“Today under the current system, they will pay over $10,000 in taxes assuming standard deductions and standard exemptions,” Cain claimed. “I’ve gone through the math -- $10,000. Now, with 9-9-9, they’re going to pay that 9% personal tax on their income, so that’s only $4,500. They still have $5,500 left over to apply to the sales tax piece, and if you go and look at how much of it they would probably spend on sales taxes for new goods, not used, used goods they don’t pay a sales tax. They are still going to have money left over, Chuck.”

But that is not exactly the case.

In fact, a family making $50,000 a year with two children would only pay about $776 in income taxes when standard deductions are factored in, based on 2010 Internal Revenue Service levels. (In fact, not factoring in deductions, a married couple filing jointly making $50,000 a year would pay $6,666 in income tax, not $10,000. But what’s important for tax purposes is “taxable” income.)

Here’s the math:

- Gross Income: $50,000
- Subtract the 2010 standard deduction: $11,400 (2011 is $11,600)
- Subtract the personal exemption (essentially the number of people in the house): $14,600 ($3,650 x 4)
- That brings us to a taxable income of $24,000
- The tax on a married couple filing jointly at $24,000: $2,766
- Then, deduct an additional $2,000 ($1,000 child tax credit x 2)

That comes out to just $766. And that doesn’t include other potential exemptions, like educator credits, moving costs, student-loan interest, health-savings accounts, etc.

Conservatives are also not thrilled with the plan, specifically because of the sales-tax piece. The sales tax without income taxes being zeroed out is something Williams says makes conservatives nervous, because they see that as a potential "spigot" the government could use when budgets get tight.

It’s unclear what this would mean for revenue yet, Williams said, adding that he would need more detail from the campaign.

It’s also unclear what exactly the sales tax would apply to. Cain this morning on The Daily Rundown said it would not apply to used items. If it applied to houses, food, and other items, that could be a significant change.

An email to the Cain campaign this afternoon has so far gone unreturned. First Read will update when we hear back.