A lot has happened since National Journal Hotline last surveyed the Senate landscape. Republicans took a significant hit when their efforts to derail the Affordable Care Act resulted in a federal government shutdown. But the struggles in implementing that law have swung the pendulum back in the GOP's favor in recent weeks.
Combined with a favorable map, Republican momentum has put control of the Senate firmly in play. In fact, the 7 seats most likely to switch parties in our latest Hotline Senate Rankings are only Democratic-held. If Republicans flip 6 of the 7 -- without losing any of their own vulnerable seats -- they would control the Senate in 2015.
Overall, 13 of the 15 most vulnerable seats are held by Democrats. Just two GOP-held seats are even somewhat in danger of flipping parties: Georgia, where Republicans could nominate a controversial candidate like Rep. Paul Broun, and Kentucky, where Senate Minority Leader Mitch McConnell isn't popular and faces well-funded primary and general-election challengers.
The seats are listed in order of their likelihood to switch partisan control after the 2014 elections. These rankings represent The Hotline's current read of the Senate landscape.
SOUTH DAKOTA (Open D, Sen. Tim Johnson retiring) (Previous rank: 1)
Former Gov. Mike Rounds is a heavy favorite to replace Johnson. Perhaps the most interesting recent development in the race is former three-term Republican Sen. Larry Pressler's potential independent candidacy. But Pressler himself admits he probably can't win, and his presence on the ballot probably wouldn't be enough to give likely Democratic nominee Rick Weiland a serious chance of holding the seat.
WEST VIRGINIA (Open D, Sen. Jay Rockefeller retiring) (Previous: 2)
Rockefeller's decision to retire handed Republicans a prime pickup opportunity in a state where President Obama received less than 36 percent of the vote last year. Rep. Shelley Moore Capito, the GOP's top choice for the race, was one of the first candidates of the cycle to announce she's running. She has raised money at a steady clip, giving her a more-than-$3-million lead over Secretary of State Natalie Tennant, who launched her candidacy in September after several other Democrats decided not to run.
MONTANA (Open D, Sen. Max Baucus retiring) (Previous: 3)
For once, Democrats might be the ones with a messy primary in a crucial Senate race. Lt. Gov. John Walsh is the favorite to capture the nomination over former Lt. Gov. John Bohlinger, but Walsh will at least have to expend resources fighting off the challenge. Both Democrats trailed Rep. Steve Daines by double digits in an automated poll conducted last week by the Democratic polling outfit Public Policy Polling. Sen. Jon Tester held onto his seat in this red state last year, but Democrats are less likely to retain control of the seat occupied by Tester's retiring counterpart, Sen. Max Baucus.
ARKANSAS (D, Sen. Mark Pryor) (Previous: 4)
Pryor remains the most vulnerable Democratic incumbent in the nation, and he's up against a top Republican recruit in Rep. Tom Cotton, who appears likely to avoid a messy GOP primary fight. While Pryor and his allies had hoped the government shutdown would weigh down the House Republican, the botched rollout of the health care law has given the incumbent an even bigger headache. Polls show a dead heat, but Pryor is running in a state that gave Mitt Romney 60 percent last year.
ALASKA (D, Sen. Mark Begich) (Previous: 5)
Begich's 2008 win is the only statewide victory to his name, and it came in a great environment for Democrats against an ethically-challenged incumbent, late Sen. Ted Stevens. Begich's run this year may prove more difficult, as he's forced to defend his vote for Obamacare in a state the president lost by 14 points last year. The good news for Begich is that a contentious GOP primary is brewing between Lt. Gov. Mead Treadwell, former Attorney General Dan Sullivan and controversial 2010 nominee Joe Miller.
LOUISIANA (D, Sen. Mary Landrieu) (Previous: 6)
We considered placing the Pelican State over Alaska in our rankings; Obama won slightly more than 40 percent of the vote in each state. But we'll put our thumb on the scale in favor of the three-term Landrieu, who's survived reelection challenges in midterm (2002) and presidential (2008) years. An all-party general election and split GOP opposition means Landrieu is a decent bet to win the general but fall short of the majority she would need to avoid a runoff. A head-to-head matchup with retired Air Force Col. Rob Maness, the favorite of insurgent conservative outside groups, would better enable Landrieu to make her centrist argument than a December date with the more moderate GOP Rep. Bill Cassidy.
NORTH CAROLINA (D, Sen. Kay Hagan) (Previous: 8)
Hagan was swept into office in 2008, along with Obama and former Gov. Bev Perdue. But North Carolina has moved away from Democrats since then: Sen. Richard Burr won a relatively easy reelection, Obama ran close but lost the state last year and Perdue didn't even bother to seek reelection. State House Speaker Thom Tillis is the nominal frontrunner in the GOP field; Karl Rove helped him raise money earlier this month. Democrats think Tillis and the GOP-led Legislature overreached this year in passing a Republican wish-list of proposals, but polls show Tillis still remains relatively unknown.
GEORGIA (Open R, Sen. Saxby Chambliss retiring) (Previous: 9)
Democrats' ability to flip this seat has less to do with likely nominee Michelle Nunn, who posted an impressive first fundraising quarter, and more to do with the potential for a disastrous Republican nominee. If controversial Rep. Paul Broun secures the nomination, the race will move a few spots up this list. For Republicans, the hope is that one of the more electable contenders, like Rep. Jack Kingston or former Secretary of State Karen Handel, can survive the likely primary runoff.
KENTUCKY (R, Sen. Mitch McConnell) (Previous: 7)
McConnell wants to be Senate majority leader, but he should first worry about his own reelection. Mitt Romney won the Bluegrass State by 23 points last year, but McConnell and Democrat Alison Lundergan Grimes are running neck-and-neck. And even before reelection comes renomination, with conservative groups taking aim at McConnell by backing political neophyte Matt Bevin. The smart money is still on McConnell, who's sitting on $10 million already, surviving. But Bevin and Grimes will come out swinging.
MICHIGAN (Open D, Sen. Carl Levin retiring) (Previous: NR)
Democratic Rep. Gary Peters is off to a good start, but former Secretary of State Terri Lynn Land, about whom Republicans weren't too excited initially, is keeping pace. Land raised $1 million in the third quarter, then backed it up with another $1 million of her own money. Peters had about $500,000 more than Land in the bank at the end of September, and recent independent polls show a tight race. But Republicans haven't won a Senate race in Michigan since the 1994 GOP wave, and Land might need a similar tide to carry her over the finish line this year.
IOWA (Open D, Sen. Tom Harkin retiring) (Previous: 10)
Democrats landed a top-flight contender in Rep. Bruce Braley, and he's lived up to the hype by stringing together impressive fundraising quarters. Meanwhile, Republicans have an overcrowded field of unknown names who have struggled to raise money. The GOP field includes some intriguing prospects, like state Sen. Joni Ernst and businessman Mark Jacobs, but the nominating process might make it difficult for either contender to win the nomination: If no candidate receives 35 percent in the primary (a likely proposition given the huge field), the nominee will be chosen at the party convention, a scenario which favors the most conservative candidates over the more electable ones.
COLORADO (D, Sen. Mark Udall) (Previous: NR)
Polls show Democrats taking a beating in Colorado, stuck between unpopular legislation at the state level and Obama's slipping national standing. Udall has been one of the more vocal Democrats upset about the health care rollout, and he's now only marginally ahead of his GOP competition. But Republicans have their own problems; 2010 nominee Ken Buck is back for another try after bungling his way to a loss against appointed Sen. Michael Bennet three years ago.
MINNESOTA (D, Sen. Al Franken) (Previous: NR)
Franken had to wait six months to take his Senate seat in 2009 after a protracted recount, but he's mostly flown under the radar thus far this cycle. The Republican field is pretty crowded, but the leading fundraiser has been Mike McFadden, whose 8-figure net worth looms as possible campaign kindling. Franken is a prolific fundraiser himself, so odds are he won't be outspent, even if McFadden emerges as his party's nominee.
NEW HAMPSHIRE (D, Sen. Jeanne Shaheen) (Previous: NR)
Just about every big-name Republican (and a number of smaller names) in the Granite State has passed on the race, leaving conservative activist Karen Testerman and former state Sen. Jim Rubens as the only GOP contenders. Former Massachusetts Sen. Scott Brown, who continues to play coy after months of visits to the state, might be the party's last chance at a competitive nominee, but GOP sources in New Hampshire doubt he'll go through with it. Even Brown would begin the race as an underdog against Shaheen, who remains one of the most popular figures in the the state.
OREGON (D, Sen. Jeff Merkley) (Previous: NR)
Merkley is facing a field of untested Republicans. But disappointment over the 2010 health care law could resonate more in Oregon, which created its own exchange but has struggled to get it started. Even if the federal government gets its website fixed soon, Oregon's portal might not be up until mid-December. One of Merkley's GOP challengers is pediatric neurosurgeon Monica Wehby, who has no political experience but could appeal to voters on the issue.