Eliminating all itemized deductions would yield about $2 trillion of additional revenue over ten years if we cut all rates by 20 percent and eliminate the AMT. Capping deductions would generate less additional revenue, and the higher the cap, the smaller the gain. Limiting deductions to $17,000 would increase revenues by nearly $1.7 trillion over ten years. A $25,000 cap would yield roughly $1.3 trillion and a $50,000 cap would raise only about $760 billion...The study does state an obvious point: the higher the cap on deductions the more it costs the wealthy. But it falls far short of the revenue "neutrality" Romney claims. If he means to achieve a twenty percent across the board tax cut as he says (today, anyway. What time is it?), and increases defense spending as promised as well, there'll need to be really drastic cuts in domestic spending. Which ones? Where? Other than PBS and Planned Parenthood, he remains silent.
...Suggesting limits on deductions was Governor Romney’s first public statement about how he might offset the revenue lost by cutting tax rates. Without more specifics, we can’t say how much revenue such limits would actually raise. But these new estimates suggest that Romney will need to do much more than capping itemized deductions to pay for the roughly $5 trillion in rate cuts and other tax benefits he has proposed.