Presidential candidates John McCain and Hillary Clinton have both recently endorsed a ìgas tax holidayî—a temporary suspension of the federal 18.4 cents per gallon excise tax on gasoline and 24.4 cents per gallon on diesel fuel—during the summer months, as a means of affording working Americans some relief from high fuel costs. The proposals differ in one important respect: Clinton would couple the temporary suspension of the tax at the pump with a windfall-profits tax on oil companies. Nevertheless, with or without an accompanying windfall-profits tax, the gas tax holiday is unjustifiable as a matter of policy, and ...