New York Times:  The Real Barrier to Tax Reform, by Bruce Bartlett:

Across the political spectrum, it is generally accepted that the basic goal of tax reform should be to broaden the tax base by eliminating tax preferences and lowering statutory tax rates. It is also believed that the principal barrier to such a reform is the resistance of special interests to the elimination of any particular preference that benefits them. But what if, to paraphrase Pogo, the special interest is us? …

[Here] are the top 10 special provisions of the tax code that reduce revenues, with the estimated annual revenue loss.

… These and other tax expenditures enjoy wide support, and it is almost impossible to imagine them being abolished, even in return for lower statutory tax rates. … President Obama and Mr. Romney have promised to protect the mortgage interest deduction. The problem is that when you take one popular deduction off the table, that becomes the best possible argument for keeping the next most popular deduction or exclusion and so on. Taking the top 10 off the table means taking more than 70 percent of the dollar value of all tax expenditures off the table, thus greatly limiting the potential for tax reform to lower rates.