Romney on deductions: I'll tell you later

One of the most strident criticisms of Mitt Romney's economic plan -- even among conservatives -- is the lack of detail on how he will support the revenue side of the government's ledger while pushing through massive tax cuts.

Romney wants to cut marginal tax rates on income by 20%. He wants to eliminate the estate tax and the Alternative Minimum Tax. And he wants to cut the corporate tax rate by 10 percentage points.

That's a lot of tax cutting. Yet Romney insists his plan will be revenue neutral -- that is, the government will collect just as much in taxes. Part of the additional revenue will result from accelerated economic growth, the campaign says, and the rest will come from limits placed on deductions, exemptions and credits currently available to top-level income earners.

Some deductions, like those available for charitable donations and interest paid on mortgages, are quite popular. So which deductions will Romney limit?

The candidate wouldn't say when he introduced the latest iteration of his tax plan in February, and he's not saying now, either. Asked by CBS host Bob Schieffer about his bashfulness, Romney punted again, suggesting that he might not even address the issue until after the election.

"Well, we'll go through that process with Congress as to which of all the different deductions and exemptions ... " Romney said before Schieffer interrupted to offer a few possible deductions that might be looked at.

But even when asked again, Romney offered no specifics.