After thoroughly beating the GOP in 2006 and 2008, 2010 seems like the last chance Democrats have to pick up some GOP Senate seats. 2012 will see a lot of the first term Dems from 06 up for reelection and we will have to play defense. For now, offense looks like the name of the game, unless you're one of the few vulnerable Democratic Senators.
Arkansas - Lincoln: Though it's often red as can be in Presidential politics, Arkansas is pretty Democratic on the state level. That having been said, Blanche Lincoln isn't looking as invincible as she did earlier this year. She did some hedging on EFCA, probably to nullify the GOP base preparing to challenge her, but this race may be one to watch once the GOP has a nominee. Luckily for Lincoln, the challenger won't be Mike Huckabee.
California - Boxer: Things aren't going well in California these days and politically things are all over the place. The budget it out of control and it looks like no one is especially popular. The interesting thing about 2010 will be the open race for Gov. happening at the same time. If the GOP can find a powerhouse for Gov., and a reputable challenger for Boxer, then she may be in trouble. If Sen. Feinstein leaves the Senate for Governor and the GOP can't recruit a strong opponent for Boxer, things will probably be much, much simpler.
Delaware - Open Seat: VPOTUS Biden's seat is pretty safe from the GOP. It's looking like his son Beau will return from Iraq and pick up where his father left off. Barring some unforseen changes, we'll have another Senator Biden come 2011.
Hawaii - Inouye: The third ranking Democrat in the Senate and the Chairman of the powerful Appropriations Committee shouldn't have any trouble winning reelection in Hawaii. He's probably safe until he retires.
Indiana - Bayh: Two term Governor turned Senator Evan Bayh is safe in Indiana, end of story.
Maryland - Mikulski: The most senior female Senator is safe from challenge is thoroughly Democratic Maryland.
New York - Schumer: Chuck Schumer shouldn't face any challenge in NY, especially since there's a much more appealing target on the ticket in 2010.
North Dakota - Dorgan: This race will be no sweat for Byron Dorgan unless Gov. Hoeven decides to run against him. Unlikely to be a nail-biter.
Oregon - Widen: Widen in unlikely to face a tough challenge, and if he is part of the movement that ultimately passes health care reform, Oregon voters will repay the favor.
Pennsylvania - Specter: Fresh from several years as a Republican, moderate Sen. Arlen Specter should win reelection in PA. He may be challenged by Rep Sestak in the Dem primary, but he has such a history in PA that Democratic primary voters will probably trust him. Toomey has no chance to beat him now.
Vermont - Leahy: Patrick Leahy will coast to reelection unless something terrible happens to the Sotomayor nomination in his Judiciary Committee and the GOP can find a stellar candidate. Chances of that are fairly slim.
Washington - Murray: Patty Murray should find her reelection campaign fairly easy with Washington trending bluer and bluer these days. She could stand to raise her profile a bit, but she's probably not in too much trouble back home.
Wisconsin - Feingold: Usually outperforming the Presidential candidate significantly, Russ Feingold should be a shoo-in for reelection. Always the chance of a major upset, but not likely.
Colorado - Bennet: When Democratic Gov. Bill Ritter picked Michael Bennet to succeed Secretary of the Interior Ken Salazar, many saw this as an opportunity to take back some GOP strength in the Mountain West. Bennet may still be in some trouble considering many Coloradans don't know too much about him, but the GOP also has a way to go in finding a credible candidate (aka Not Tom Tancredo). Depending on who they choose, this could be a contested seat, or it could be a less than challenging fight.
Connecticut - Dodd: If you would have mentioned to me last year that Chris Dodd's name would appear on any list of vulnerable Senators I would have laughed out loud. The collapse of the banking system (he's chair of the Banking Committee) and a scandal involving a sweet deal mortgage have hurt Dodd to the point that several Republicans are looking to challenge him. CT is still pretty reliably Democratic these days and Dodd still has some time to bolster his image at home. Maybe the economy will pick up again and he'll coast to reelection. If not, he may find himself out of a job.
Illinois - Burris: Who knows if Roland Burris will even run for reelection, but if he does, he certainly won't win the Democratic Primary. Up against Rep. Schakowsky and Treasurer Giannoulias, not to mention a Kennedy, Burris is looking more and more like a seat warmer. This is probably a safe bet for Democrats, and it's safer yet that that Dem won't be named Roland Burris.
Nevada - Reid: It's strange how Democratic leaders find themselves in such hot water when it comes to reelection. Daschle got knocked off in 2004 and now Reid is looking terribly vulnerable. His numbers are down and the GOP is salivating about grabbing this seat. Unfortunately for them, the GOP prospects are slim. Those who aren't in corruption scandals of their own may not want to go up against Reid who does have the possibility of calling in the big guns (like POTUS) for fundraising and campaigning, because we all know Mr. President would like to keep Nevada as blue in 2012 as it was in 2008.
New York - Gillibrand: Succeeding Hillary Clinton is no easy task and Kirsten Gillibrand has found herself under fire from lots of potential challengers. Most of them are from within her own party of gun rights or other issues. If she can survive a primary challenge (which thanks to some help from the White House, she probably will) then she has a good shot at hanging on. Of course we can't predict what will happen until we know who the GOP challenger will be.