The legendary political analysist Larry Sabato writes a long history of post-WWII midterm elections, and comes to the conclusion that presidential approval ratings were the mitigating deciding factor in most of them.
What makes a midterm historically memorable? All of these elections involved two or more of the following critical factors:
* Exceptional presidential poll ratings (either unusually low or high)
* Foreign war (popular or unpopular)
* Sour economy
* Major scandal
* Intense hot-button social, domestic issues
The problems bedeviling Bush and the GOP may get a bit better or a little worse, but they appear to be intrinsic to this election year. Therefore, the only real question is how many seats the Democrats will gain in the Congress and the statehouses, not if they will gain.
Sabato sees potential Republican losses as low as 5 seats in the House, which would leave a weakened-but-still Republican majority in control for the end of the Bush era, and Democrats' hands far away from the subpoena drawers. Both parties will get a sense of the playing field in five days, when voters in Randy "Duke" Cunningham's old California seat go to the polls. A Democrat, Francine Busby, has even odds of winning a district that voted for Bush by 15 points. If that happens, all this analysis of Republican doom will start to be taken seriously.