Almost everyone thinks we should broaden the tax base; that is, reduce the number and size of tax deductions, exclusions and credits.

The Bowles-Simpson fiscal reform plan went after tax breaks so aggressively it was able to slash the deficit and still cut tax rates. Most conservative reformers follow that model. Even economists who aren’t conservatives generally say the government should raise revenue by getting rid of tax breaks before it raises rates. That is the position Republican leaders in the House and Senate have taken, too.

As pleasing as it is to find a consensus in this polarized era, this one is mistaken. It would be either undesirable or politically impossible to reduce the largest loopholes in the code.