Senator Tom Coburn, the conservative Republican from Oklahoma, is doing something mischievous, clever, and important. Coburn is a key player in bipartisan negotiations to reduce the medium-term deficit. Everybody understands that a deal like this can only happen via some combination of spending reductions and revenue increases. The latter part violates sacred GOP theology, and the high priest of this theology is Grover Norquist. Through Americans for Tax Reform, Norquist has gotten most Republicans to sign a pledge never to increase tax revenues for any reason. Coburn is attempting to expose the ridiculousness of this pledge.

Of course, he's not exactly saying that. His whole fight with Norquist is being conducted in the language of movement conservative cant. But he is doing something quite daring.

The revenue increase Coburn is considering, as outlined in the Bowles-Simpson plan, would, one way or another, reduce tax expenditures. It would not increase tax rates -- indeed, it would lower them -- but it would instead claw back the vast array of tax deductions that reduce revenue by more than a trillion dollars a year. This would violate the Taxpayer Protection Pledge. the Pledge is not about rates, it's about revenue. Norquist wants people -- and especially rich people -- to pay less money to the government. To Norquist, eliminating a tax loophole is just as bad as raising rates. So he opposes any attempt to increase revenue through the elimination of loopholes, however unworthy those loopholes may be.

Norquist and Coburn have been circling each other for months, trading barbs in the media. Now Coburn is using a test case to expose Norquist's Pledge. That test case is the ethanol subsidy, which is pork that survives due to the strength of the agriculture lobby, but which the conservative movement at least putatively opposes. The ethanol subsidy, like many subsidies, comes in the form of a tax break. Eliminating it is, therefore, a tax increase. Therefore, eliminating the ethanol subsidy, without using the revenue for a tax cut, would violate the Pledge.

In other words, Coburn has set a trap for Norquist. He has proposed eliminating the ethanol subsidy. If Norquist supports it, he has to alter his pledge to allow for closing loopholes that raise revenue. If he opposes it, he has to admit that he opposes closing loopholes that even Norquist admits are unsupportable. Norquist's response? He opposes closing the loophole:

Sen. Tom Coburn (R-Okla.) ripped conservative activist Grover Norquist on Tuesday for defending tax breaks that benefit special interest groups. 
In a letter to Norquist, the president of Americans for Tax Reform, Coburn said a tax break for ethanol producers ultimately raised the tax burden for average taxpayers and should be done away with.
Americans for Tax Reform quickly shot back with a letter to Coburn that accused the senator of misinterpreting its views of the ethanol tax credit, which it said it opposed. The group said it opposed Coburn’s amendment because he did not offset elimination of the tax break with a corresponding tax cut.

So now the trap is sprung. Coburn can now paint Norquist's pledge as un-conservative -- it's protecting pork and special interest subsidies that conservatives oppose. And Coburn is right! Assuming, of course, that you define conservative to mean a belief in low nominal tax rates and a tax code that doesn't pick winners or losers, as opposed t a tax code that raises the smallest amount of revenue as possible from rich people.

The implications of Coburn's fight is profound. Norquist's vision of conservatism has completely dominated the Republican Party for twenty years. Nobody has even attempted to push back. Coburn may not win, but the mere fact that he is opposing Norquist's definition of proper party dogma is highly significant.