The wave of moderate departures isn't confined to the Senate. There is a decent chance that the six most conservative Democrats in the House won't return to the next Congress: Reps. Dan Boren, D-Okla., and Mike Ross, D-Ark., will retire; Rep. Joe Donnelly, D-Ind., is running for Senate; and Reps. Jim Matheson, D-Utah, Jason Altmire, D-Pa., and Mike McIntyre, D-N.C., all face tough re-election bids.
The roster of the most liberal Republicans in the lower chamber is heavy with Democratic targets. Reps. Charlie Bass, R-N.H., Pat Meehan, R-Pa., Michael Grimm, R-N.Y., and Joe Heck, R-Nev., are just a few of the more centrist Republicans that Democrats will aim to defeat this year.
Snowe first won her Senate seat in the Republican landslide of 1994, though she made her name by carving out a niche in the center, rather than on the right. It's likely her successor -- and Nelson's, and Lieberman's, and most new House members elected this year -- won't follow that same model.