The CBO notes that this idea is not something it just dreamed up. Four years ago, a tax reform advisory commission appointed by President George W. Bush came up with a similar recommendation to transform the mortgage deductions into a credit. The attractiveness of the credit concept is both fiscal -- it raises a boatload of new money for the government -- and social.

Besides raising $13 billion in 2013, CBO estimates that moving to a credit approach would increase revenues by nearly $390 billion between 2013 and 2019. Equally important, the credit plan would also please critics who say the current tax system shortchanges lower- and moderate-income homeowners, and encourages Americans to overspend on massive houses loaded down with monster-sized mortgages.

Though the CBO concedes this option might also have negative side impacts on the real estate market -- fewer sales, less money spent on construction, lower home values at the upper end -- it's not clear what effect it would have on the national rate of homeownership. Why? The report notes that Canada, the United Kingdom and Australia all have roughly similar homeownership rates as the United States, but none provide mortgage interest tax deductions.

Other housing-related items on the CBO's revenue-raising target list:

-- Get rid of all write-offs for state and local taxes, including property taxes. That would pump $343 billion into federal coffers between 2010 and 2014, and $862 billion by 2019.

-- Clamp a 15 percent cap on the value of all itemized deductions -- not just mortgage interest and property taxes but charitable contributions, medical expenses and casualty losses. The revenue windfall: $1.3 trillion over 10 years.

-- Revert to the capital gains approach that prevailed before 1987. Rather than taxing most gains at 15 percent as the current code does, the CBO plan would exclude 45 percent of gains from taxation, and tax the remaining 55 percent at an individual's regular tax rate. New money raised: $48 billion over the next decade.

Where's all this headed? That depends. The mortgage interest deduction has been a political no-go zone for decades. The same for local property tax write-offs. But with billowing deficits, and trillions to raise to help pay for health care reform and the economic stimulus bills, somewhere, somehow, Congress is going to be pressed to raise revenues.

Even no-go zones could get new scrutiny.