Remember the flat tax? The policy proposal gained traction among conservative politicians for a while in the 1990s, but it withered amid little real-world political support.
Now it's back, as a fiscal policy cornerstone of Kansas Sen. Sam Brownback's campaign for the 2008 Republican presidential nomination.
It calls for earned income to be taxed at the same marginal rate, unlike the current system, which has different tax brackets for different incomes. Typically, proponents of a flat tax call for eliminating most deductions except for a sizable individual exemption.