How much of Herman Cain’s gravity-defying popularity has to do with his tax plan? Quite a bit, it seems. According to a new Des Moines Register poll, 29 percent of likely Republican caucus-goers in Iowa think they’d be better off under Cain’s 9-9-9 tax plan, with just 18 percent saying they’d be worse off. And, despite evidence that the plan is sharply regressive, the plan’s even more popular among Iowa Republicans making less than $50,000, with 34 percent saying they’d be better off.

Herman Cain (Source: Getty Images)

At the same time, Cain could argue that pro-9-9-9 Republicans believe that his tax plan would bring broader benefits to the economy by lowering taxes on businesses and making the tax system consumption-oriented, as he’s argued. Sandvic, the poll participant, told the Register that under 9-9-9, “it’s possible employers would pay employees more if the employer pays less in taxes...and tangible goods could cost less because of lower corporate taxes.”

The poll—which showed Cain leading Romney by 23 to 22 percent — was taken before the allegations of sexual harassment became public. But the latest numbers since the scandal show that Cain’s popularity has actually ticked up slightly, nationwide. So the centerpiece of Cain’s campaign, the 9-9-9 plan, could matter in Iowa and elsewhere.