3. Timing. The best way to have a wave election is to have the other party control the presidency during a bad economy or some kind of major scandal. Democratic waves in 2006 or 2008 owed a great deal to the non-existent income growth during the Bush years. The GOP wave owed a great deal to the economic crisis. But in 2012, Democrats will still have the White House, so they won’t benefit from an anti-incumbent wave. (They may pick up some seats due to sporadic voters re-engaging.) The best hope of a big wave would come from a deep and extended economic crisis that gives Republicans control of government in 2012, continues through 2014 and paves the way for a midterm backlash. But that’s not exactly a positive scenario.

As long as Republicans control the House, the prospects for progressive or even good-government technocratic legislation (to reduce the deficit or reform the tax code, say) are probably nil. So enjoy the legislative triumphs of Obama’s first two years, because that’s going to be it for a while.