There's a similar phenonmenon when you poll people about reforming the individual income tax system. I remember back in the Armey flat tax days in the mid-1990s(remember H.R. 1040?) when the polls showed high approval for moving to a "postcard-sized" tax return and even that single marginal tax rate (above exemption), but when in the same poll folks were asked whether they'd be willing to give up their particular itemized deductions (e.g., the mortgage interest deduction) in exchange for the lower marginal tax rate, they balked.