The Norquist Puzzle

Many Republicans are doing cartwheels to explain why they have abandoned the Norquist tax pledge. But I don’t quite understand why. If a bill to extend the Bush tax cuts for people who earn under $250,000, I would think a signer of the pledge would be obligated to vote for the extension. Similarly, if a bill to extend the Bush tax cuts for those who earn over $250,000, I would think, a signatory to the Norquist pledge would be obligated to vote for it (though it would have no chance of passage. What the pledge by its terms would seem not to permit is holding the majority of the country hostage to the rich. The pledge by its terms makes no such distinction.