Everyone knows we need to reach that magic number of 60 to truly be safe from the Republican obstructionism. Right now, on most votes, we have a solid 49 in place. Lieberman, on war, bankruptcy and Alito votes for cloture (on war much worse than that), so you can't count on him on key issues (and he may yet joing the GOP).
Ben Nelson really is a Republican (his "composite liberal score" is not only below 50%, but below any other Democrat by double digits. Meanwhile, Olympia Snowe, Susan Collins, Gordon Smith, Norm Coleman, Dick Lugar and former Senators Lincoln Chafee and Mike DeWine all possess higher liberal scores--with John Warner and John McCain just about in a tie with Nelson).
So with that in mind, go check out Swing State Project's look at potential Republican retirements. Domenici's potential legal woes have to be weighing on his decision (not to mention an increasingly more liberal state, his age, etc.), and the changing environment in Virginia has to be making John Warner rethink his pledge to run again.
Add in Allard (who already said he is retiring, which means someone else will have to make up for his...I mean take up his passionate fight for...ok, just possess his title), and that is potentially three open seats in states in which Democrats have often been winning lately. So then you look at Collins, Smith, McConnell, Dole, and Coleman, in what again may be a horrendous year for the GOP (unless they can find some more attorneys to concoct "voter fraud" charges or find their way out of Iraq--sadly, doubtful) and we're getting closer. A solid challenge to Lamar Alexander and another potential open seat in Mississippi could make it even more interesting (if popular former AG Mike Moore runs).
I have written more than intended. Read the piece.