Races are ranked in order of their likelihood of changing parties (by November 2010, accounting for all factors such as potential retirements, primary challenges, and so forth.
Likelihood of party switch has increased since last month‘s rankings.
Likelihood of party switch has decreased since last month.
1. 
New Hampshire (R-Open)
Pennsylvania and New Hampshire had been battling back and forth for the #1 slot for the past couple of months. With the landscape in the Keystone State completely changing after Arlen Specter’s defection to the Democratic party, New Hampshire now has the stage to itself — although there’s some marginally bad news for the Democrats in the form of Paul Hodes’ underwhelming fundraising numbers. Hence, the downward-pointing red arrow. Still, this looks like the cleanest path either party has to a pickup, with an open seat in a Democratic-leaning state.
2 .
Missouri (R-Open)
In Missouri, conversely, the money numbers favor the Democrats, with Robin Carnahan having out-fundraised Roy Blunt about 2:1 in the first quarter. Although Missouri has gradually trended red at the Presidential level, Carnahan may simply be the more talented candidate and this increasingly feels like a lean Democratic race.
3. 
Connecticut (D-Dodd)
We’re waiting for some fresh polling to see whether Chris Dodd has broken free at all from his post-AIG doldrums. In the meantime, GOP challenger Rob Simmons reported raising just $20 in the first quarter. But that might not matter, since the important thing about Rob Simmons is not that he’s Rob Simmons but that he’s not Chris Dodd.
4. 
Kentucky (R-Bunning)
A Jim Bunning retirement would help Republicans — but perhaps not as much as you’d think in a state where Democrats still have a significant registration advantage. In addition (as with most things having to do with Jim Bunning), it’s far from clear what’s actually happening with respect to his retirement.
5. Ohio (R-Open)
Ohio is in perhaps the most advanced state of any of the 2010 races, with likely GOP nominee Rob Portman having raised $1.7 million in the first quarter and Lieutenant Governor Lee Fisher, one of two main Democratic rivals, countering with more than $1 million of his own.
6. Florida (R-Open)
We’re hearing from Florida Republicans that nobody is quite certain whether Charlie Crist is in fact going to enter the Senate race — possibly including Crist himself. Until we have news of his decision, this race is stuck in something of a holding pattern.
7. North Carolina (R-Burr)
Likewise in the Tarheel State, we’re waiting on word from Democratic Attorney General Roy Cooper, whose entry would turn the race against unremarkable incumbent Richard Burr into a toss-up.
8. 
Delaware (D-Open)
Last month, we touted Delaware as a sleeper, pointing out that Republican Mike Castle, currently Delaware’s at-large representative to the House, had an 8-point lead on likely Democratic nominee Beau Biden. Now, it looks like Castle’s interest in the race may be more than hypothetical, as he told Roll Call that he’s more likely to run for Senate than for re-election to the House. That statement can be interpreted in different ways since Castle, 69 years old and a stroke survivor, could easily choose retirement instead. But Democrats had better keep a close eye on this one or Joe Biden (assuming he’s gotten over his fear of public transportation) is going to be spending a lot of time on the Acela commuting back to Wilmington to campaign for his son.
9. 
Colorado (D-Bennet)
Colorado moves up for the second consecutive month, this time on mediocre polling for Democratic pseudo-incumbent Michael Bennet, who has a net-negative approval rating and had better hope that the GOP doesn’t organize around a strong opponent.
10. 
Illinois (D-Burris)
This is no longer the Roland Burris show, who polls at just 46 percent approval among African-American voters, just 29 percent among Democrats, and just 17 percent overall. But Lynn Sweet reports that IL-10’s Mark Kirk is leaning toward an entry in the race, and Public Policy Polling has him competitive against several prospective non-Burris Democrats (although AG Lisa Madigan, probably bound for the governor’s race, would crush him if she ran). In the long run, this race will probably gravitate toward the Democrats as candidates like Alexi Giannoulias improve their name recognition and the Blagojevich affair fades from memory. But it’s a long way to the finish line, and Kirk is one of the few Republicans to have found electoral success in a Democratic-leaning district.
11. 
Nevada (D-Reid)
As Republicans scramble to find an opponent in what should be a good opportunity for them, Harry Reid has been busy raising money and now has more than $5 million in cash-on-hand.
12. 
Pennsylvania (R- D-Specter)
In some sense, this was the first victory of the 2010 cycle for the Democrats — although considering Specter’s voting record thus far, it looks as though it might be something of a Pyrrhic one. Nevertheless, this is now considered a Democratic seat, and this rating now reflects the Republicans’ odds of winning it back in 2010, either against Specter or another Democrat like Joe Sestak.
A Republican comeback is unlikely if the uber-conservative Pat Toomey is the Republican nominee. But if ex-Gov. Tom Ridge runs — and wins — instead, he would be a formidable opponent. The catch is that it isn’t clear how Ridge, like Specter a moderate, pro-choice Republican, will escape the problems that drove Specter from the party, as what’s left of the GOP base in Pennsylvania is highly conservative and pro-life. We should know more in a week or so — if you’re a Pennsylvania voter and weren’t at Citizens’ Bank Park watching the Phillies and the Mets get rained out, you were probably getting nonstop phone calls from pollsters.
13. 
Texas (R-Open?)
Which is more likely — that the last-place Houston Astros win the NL Central, or that Kay Bailey Hutchison is still in the Senate by June, 2010? Start printing those playoff tickets, because every indication we’ve heard and seen is that Hutchison is leaving the Senate to challenge incumbent governor Rick Perry, which would leave this race wide open. Democrat Bill White, the mayor of Houston, is raising serious money, while state former comptroller John Sharp is bankrolling his own million-dollar stake into the race.
14. Louisiana (R-Vitter)
This race is a Big Shiny Object which we continue to believe has been overrated by some other authorities. There is some rather ambiguous new polling out on Vitter, who retains a reasonably high approval rating in spite of the fact that many Louisanans would consider replacing him. The questions are how many of those Louisianans would consider replacing him with a Democrat in a state that increasingly leans red, particularly given that the Democrats are a long way from having identified a challenger.
15. 
Iowa (R-Grassley)
Once we get down into the mid-teens, we’re basically looking for excuses to flag a race, and the fact that Grassley raised less than $300,000 in the first quarter makes us wonder just how certain Republicans can be that Grassley won’t follow colleagues like Kit Bond and George Voinovich into retirement. If Grassley were to retire, then the Democrats, who might find willing candidates like Tom Vilsack, Chet Culver and Bruce Braley, would presumably become the favorites.
16. New York (Jr.) (D-Gillibrand)
New Yorkers remain highly skeptical of Gillibrand, but Republicans have at least three hurdles to overcome before defeating her. Firstly, Gillibrand is raising boatloads of money. Secondly, David Patterson is far more vulnerable than she is and will draw some of their talent away to the gubernatorial race. And thirdly, New York is still a highly blue state, as Jim Tedisco’s inability to win in NY-20 (perhaps the Republicans’ best district in the state) would tend to attest. Although George Pataki or Rudy Giuliani could make things interesting, Gillibrand is probably more vulnerable in the primaries than in the general election.
17. 
Arkansas (D-Lincoln)
Lincoln raised $1.7 million in the first quarter, which may further reduce the mostly-theoretical possibility that Republicans decide to mount a serious challenge to her.
18. 
Oklahoma (R-Coburn)
Some sleeper potential here, as Coburn raised virtually no money last quarter and seems exceptionally indifferent to the prospect of running for re-election. That could open the door to popular Democratic Governor Brad Henry or perhaps U.S. Rep. Dan Boren, who has dropped hints that he might be interested in an open-seat race.
19. California (D-Boxer)
I’d been so fixated on the Governator that I missed the fact that there has been some polling of Boxer versus Carly Firoina, who now seems like the more likely opponent. The Field Poll put Boxer ahead by 30 points in that matchup, whereas Rasmussen had her up by just 9 — so goes it with polling this far in advance of an election. Although California is a tough state to gauge, Fiorina did not prove to have particularly adept political instincts while taking her turn as a spokesperson for the McCain campaign, and her fundraising base may also overlap heavily with that former eBay CEO Meg Whitman (who is getting serious about running for governor). I don’t see it, frankly, but Boxer, who had a somewhat disappointing fundraising quarter, will need to remain on her toes.
20. 
Georgia (R-Isakson)
Well, there’s new polling to suggest that Isakson could be vulnerable, but we remain a little skeptical after seeing what happened to Jim Martin once Barack Obama’s name was off the ballot.
21. 
Wisconsin (D-Feingold)
Although previous approval polling had suggested some vulnerability for Feingold, SurveyUSA’s latest installment has him at a relatively healthy +18 net. Feingold’s strongest potential challenger, the conservative-but-telegenic Paul Ryan, also recently told the Milwaukee Journal-Sentinel that he wouldn’t run against Feingold (reading between the lines, Ryan seems inclined to wait for Herb Kohl to retire instead).
22. Arizona (R-McCain)
Unlike Pennsylvania, Arizona retains a relatively broad and diverse Republican base, and so we don’t see much risk of the Republicans getting Toomeyed by Minuteman founder Chris Simcox, who will challenge McCain in the primary.
23. Kansas (R-Open)
All the action is on the Republican side, as Kathleen Sebelius was finally confirmed to HHS and the Democrats don’t yet have a declared candidate.
24. Hawaii (D-Inoyue)
25. Alaska (R-Murkowski)
26. 
North Dakota (D-Dorgan)
A nice 1Q fundraising haul by Dorgan reduces the already-slim chance that popular GOP governor John Hoeven might decide to challenge him.
27. Maryland (D-Mikulski)
28. South Carolina (R-DeMint)
29. Washington (D-Murray)
30. South Dakota (R-Thune)
31. 
Alabama (R-Shelby)
Shelby’s approval ratings are surprisingly marginal, but don’t hold your breath.
32. Indiana (D-Bayh)
33. Vermont (D-Leahy)
34. Oregon (D-Wyden)
35. Utah (R-Bennett)
36. New York (Sr.) (D-Schumer)
37. Idaho (R-Crapo)