Herman Cain, under assault by conservatives and mainstream analysts on the defects in his 9-9-9 tax plan, is now offering another iteration, one that his advisor Rich Lowrie told Right Turn was in the works. The Associated Press reports:

After sharp criticism over his one-size-fits-all plan from Republicans and Democrats alike, Cain was set Friday to propose exemptions for businesses investing in “opportunity zones” as a way to give an economic jolt to rundown neighborhoods. He’s also proposing new tax brackets to reflect different income levels.

Up to now, Cain has touted a plan to scrap the current taxes on income, payroll, capital gains and corporate profits and replace them with a 9 percent tax on income, a 9 percent business tax and a 9 percent national sales tax. But the plan seems to be unraveling. . . .

His plan, however, was a significant adjustment from how it was initially proposed. In an interview last week, he suggested some leeway to boost economic development. For instance, taxes in struggling areas could be set at 3-3-3 rates, 3 percent in each category.

“Because you have a lot of African-Americans located in cities like Detroit — disproportionately — it would encourage businesses to stay in business there or to move there,” Cain told CNN. “It would encourage people to work there, because if you live in the empowerment zone, you’re going to pay a smaller percentage in taxes.”

To begin with, I don’t know what the numbers of African American have to do with anything, especially for a candidate who disclaims interest in racial politics.

But the problem is worse than that, of course. He’s now piling complication on top of complication and removing one feature that he previously touted, namely that everyone pays the same rate. It also suggests that he and his advisor have rethought their disdain for progressivity in the tax code, which Lowrie expressed to me a little over a week ago. After telling all critics that they were simply “wrong,” this is no doubt a painful admission that the plan was becoming a hindrance, not a help, to his campaign.

Conservatives’ patience with Cain is wearing thin. Social conservative leader Gary Bauer e-mailed me before the latest course correction: “I am sure Herman Cain’s thrust into the spotlight has been a challenge to process. Regular statements of clarification are not a good way to run a campaign. From the battle over life to negotiating with terrorists there are people who wish him well who could help him navigate these important issues. He needs to talk to them now.” It’s not clear who his advisers are because that’s a secret, he tells us. What is that about?

Texas Gov. Rick Perry is due out with a flat tax plan. The Cain experience should be instructive for the Perry camp. Make sure the math is right. Don’t shift the tax burden from corporations to individuals or from rich to middle class (or poor). Make sure it really is revenue neutral. And be prepared to respond to all manner of questions without sounding defensive. Perry reportedly has some pro-growth all-stars working on the plan; it should be interesting to see what they come up with.

As for Cain, this has been one of the worst weeks for any candidate in the campaign. Whether he can regain his footing depends on eliminating errors, upgrading staff, studying up on foreign policy and, frankly, sticking to a script. Right now the impression is growing that he simply doesn’t know what he is doing.