South Dakota: Johnson is extremely vulnerable even if he runs for reelection. His health could prevent him from running an active and energetic enough campaign to beat Rounds (Rounds can be beaten, but it would require a major effort on Johnson's part). Rounds could be vulnerable on abortion though (especially if Johnson is pro-life, which would give him some cover when attacking Rounds on that ballot measure he supported). My guess is that either Johnson doesn't run for reelection and Rounds wins by a solid margin (something like 58%) or Johnson runs and Rounds narrowly wins after leading by 2-3 points for the last few months of the campaign.
Alaska: Begich is obviously quite vulnerable, but he is also an extremely strong and energetic campaigner. He has already suggested that he wants to make social security a major issue in the campaign. Some of this depends on who the Republicans nominate, Pernell would win, but he probably won't run. Joe Miller might run, but Begich could definitely beat him. The rest are unknowns to me. The tea-party could hurt the Republicans here if they get someone like Miller nominated. Until we have some idea of who is running, I can't predict this one.
Louisiana: Landrieu is a strong candidate with many of the right interest groups in her corner. But the likely Republican nominee, Bill Cassidy, seems like a strong candidate and the state's political trend is on his side. This one could be a real nail-biter.
Arkansas: I think Pryor will win, he seems to be in good shape. The Republicans could force the Democrats to spend some money here though.
West Virginia: If Rockefeller retires and Capito is the Republican nominee, this could be a problem for the Democrats. However, Capito is not as unbeatable as she is sometimes made out to be and the right type of Democrat could beat her. I could see the tea-partiers blocking Capito's nomination or just discouraging her from running (she seems to be waiting for an easy race). McKinley might actually be more likely to run. He'd also be a strong (but beatable) candidate, but I don't think he'd scare strong Democrats away from the race the way Capito might. If Rockefeller runs, he wins, but by less than he has in the past. Capito won't run against Rockefeller; McKinley run and would make the Democrats (or at least Rockefeller) spend money, but he'd narrowly lose. If McKinley and Capito sit this one out, then the Republicans will be out of luck here. I can't say more until we know who is running.
North Carolina: Depends who runs, the tea-party could really screw the Republicans here. The Republicans need someone in the mold of McCrory. Can't say much until we know who is running.
Kentucky: Depends who runs and even then it would be a tough race, but McConnell is beatable with the right candidate. At the least, the Democrats can make the NRSC waste tons of money here. McConnell has the early advantage though and I doubt he'll have more than token opposition in the primary.
Iowa: If Harkin runs, he wins. Even in an open seat, I think the Republicans would have a lot of trouble winning the seat. Steve King is acting like he wants to run and he'd win the primary, but have no shot in the general. Latham could win, but I don't see him running (or winning a statewide primary against King, for that matter).
Montana: Baucus has recovered somewhat from the healthcare debate and the Republicans have a surprisingly weak bench here. Baucus has the early advantage...somehow
Maine: If Collins retires its a Democratic pickup, if she runs then she wins.
New Hampshire: Shaheen should win; the Republicans might make the Democrats spend money here, but even that is iffy.
