Update: Important point from Steve Benen:
In the House, 14 GOP incumbents have decided not to seek re-election, while 10 Democratic incumbents have made the same announcement. Does this mean Republicans are "dropping like flies"?
In the Senate, six Republican incumbents have decided not to seek re-election, while two Democratic incumbents have made the same announcement. Is this evidence of a mass Democratic exodus?
Among governors, several incumbents in both parties are term-limited and prevented from running again, but only three Democrats who can seek re-election -- Parkinson in Kansas, Doyle in Wisconsin, and Ritter in Colorado -- have chosen not to. For Republicans, the number is four -- Douglas in Vermont, Rell in Connecticut, Crist in Florida, and Pawlenty in Minnesota. (Update: the GOP number is five if we include Palin in Alaska.)