Chris Beam has a nice piece [link now included] at Slate that takes on the whole “oh, what a terrible year for incumbents!” notion and shows it to be mostly wrong. There’s a cite to my post from a while back, but this is the real money:
bq. But let’s put this in perspective. So far this year, 282 federal-level incumbents have been up for re-election. Of those, only six have lost their seats—four in the House and two in the Senate. (Aside from Bennett, Kilpatrick, and Specter, there’s Rep. Alan Mollohan, D-W.Va.; Rep. Parker Griffith, R-Ala.; and Rep. Bob Inglis, R-S.C.) That’s 2 percent of all incumbents. If you count only the 119 incumbents who have faced primary challengers, the proportion who were defeated goes up to 5 percent.
Kudos to Beam for actually counting both the numerator and the denominator and then dividing. That bit of simple arithmetic seems beyond a great many commentators.