Today's Washington Post takes Senator John McCain to task for promising unsustainable tax cuts, including making permanent President Bush's tax cuts, repealing the AMT, making permanent the research and experimentation tax credit, cutting the top corporate tax rate from 35 to 25 percent, and allowing businesses to immediately write off all capital investments (rather than depreciating them over time). He has also proposed to require a super-majority vote in Congress for any tax increases. (Last week, TaxVox raised its own questions about how tough it would be for McCain to keep his tax cut promises.)