The Romney idea is certain to face headwinds from various interests such as the real estate industry and nonprofits that rely on charitable contributions. Obama has repeatedly proposed limiting tax deductions for the wealthy so that each dollar of deduction does not cut their tax bill more than 28 cents - the same rate paid by many middle-class taxpayers - as opposed to the 35 percent rate they pay today.
Conservative groups, Republicans and charities opposed the idea, warning it could hurt charitable giving.
But Romney's proposal is far more extreme. In his own case, he has taken millions of dollars in tax deductions from his charitable donations. A $17,000 cap would increase his own tax bill substantially as a result.