Safe Republican Seats: Alabama, Georgia, Idaho, Kansas, Mississippi, Nebraska, Oklahoma, Tennessee, Texas, Wyoming
Kentucky-Senate Majority Leader Mitch McConnell may face a primary challenge from his right. There really isn't a logical basis for this, but it may very well happen anyway. McConnell is a savvy politician with a massive war chest. He's also avoided any votes that could be used against him. I don't take a potential challenge very seriously, although a deal with President Obama to raise taxes could completely alter this outlook.
Maine-Susan Collins is the last of the moderate New England Republicans. Her ideological twin Olympia Snowe retired last year. It is possible Collins will do the same. If she does not she will most likely face a primary challenge. The Maine Republican primary electorate is quite conservative, a serious challenger would stand a real chance. If Collins is not the Republican nominee Democrats will be strong favorites to win this seat.
South Carolina-Lindsey Graham is the best candidate to be this cycle's Richard Lugar. Graham is conservative, but not as conservative as you would expect a Senator from South Carolina to be. He has shown a willingness to work with Democrats on immigration, climate change, and other issues. He also voted to confirm both Sonia Sotomayor and Elena Kagen to the Supreme Court. Graham is a ripe target for a primary challenge and would probably be a slight underdog. Regardless of who the nominee is, this seat will be won by the Republicans.
Safe Democratic Seats: Delaware, Illinois, Massachusetts, Michigan, New Jersey, New Mexico, Rhode Island, Iowa
Possible Democratic Retirements:
Michigan-Carl Levin will be 80 years old in 2014. He has not announced whether or not he will seek re-election. If he retires, competitive primaries are likely on both sides. Possible Democratic candidates include Mark Schauer, Gary Peters, Virg Bernero, Bart Stupak, Dan Kildee, Gretchen Whitmer, and Jocelyn Benson. Possible Republican candidates include: Justin Amash, Mike Rogers, Candace Miller, Bill Schuette, Bill Huizenga, and Dan Benishek. This seat would be a toss-up barring one of the parties nominating a weak candidate.
New Jersey-Frank Lautenberg will be 90 years old in 2014. Needless to say he is likely to retire. This seat is similar to Michigan: a toss-up if the popular incumbent retires. If Cory Booker passes on running for governor in 2013 I would look for him to emerge as the top contender for the Democratic nomination.
Alaska-Mark Begich won a narrow upset victory over convicted felon Ted Stevens in 2008. Obviously, Begich starts this race as an underdog. He won't be facing a convicted felon this time. The best he could hope for is Tea Party lunatic Joe Miller. Assuming Republicans nominate a sane candidate they will probably win this race. Rating: Leaning Republican
Colorado-This seat appears to be safe. Mark Udall is very popular and the demographics are improving in Colorado for Democrats every year. Former Governor Bill Owens would be able to mount a strong challenge. Barring Owens entering the race, this looks good for Democrats. Rating: Strongly Democratic
Minnesota-Al Franken is a conservative boogeyman, but he has kept a low-profile in the Senate and maintains high approval ratings. Minnesota is a solidly blue state and there does not appear to be a strong Republican candidate on the horizon. I would rate this as Strongly Democratic
New Hampshire-Jeanne Shaheen won a fairly narrow victory in 2008. New Hampshire is typically blue in presidential years but more conservative in midterm elections. I forsee a tough fight ahead to keep this seat. Rating: Toss-up
New Mexico-Tom Udall won with 61% of the vote in 2008. New Mexico is getting bluer every single year. Republicans failed to mount much of a challenge for the other seat in 2012. I don't expect much trouble for Udall here. Rating: Strongly Democratic
North Carolina-Kay Hagen upset Elizabeth Dole with 53% of the vote in 2008. Hagen ran ahead of President Obama by four points in 2008. President Obama lost North Carolina by 4% last week, showing that this will be a tough race. A midterm electorate makes the state even more formidable. If Republicans can find a candidate here they should be favored. Rating: Leaning Republican
Oregon-Jeff Merkley won a close race in 2008 with 49% of the vote. Oregon has gotten bluer in recent years but remains a winnable state for the right kind of Republican. I would expect a close race here. Rating: Toss-Up
Virgina-Mark Warner is extremely popular. It's unlikely Republicans will be able to mount a challenge to him. Rating: Strongly Democratic
Arkansas-This state kicked out its other Democratic Senator in 2010. Mark Pryor is likely to suffer the same fate. Pryor will surely mount a strong campaign, but the conservative movement in the state seems to great to overcome. Rating: Leaning Republican
Louisiana-The exact same story as Arkansas. Louisiana has gotten much more conservative in recent years. Mary Landrieu was only able to win 52% of the vote in 2008 despite a national Democratic wave. I'm not seeing a path to victory for the Democrats here with an implosion of Todd Akin/Richard Murdock levels. Rating: Strongly Republican
Montana: Montana will vote for the right kind of Democrat. John Tester proved that by winning re-election last week. The problem for Max Bauchus is that he put himself at the center of the healthcare reform debate and alienated many of his constituents. Comparatively, Tester stayed quiet and didn't see the same drop in his approval ratings. This should be a tough race. Rating: Leaning Republican
South Dakota: Tim Johnson has had health issues in the past, making his retirement a possibility. If he chooses to run he will face a tough challenge. The Dakotas are winnable for a strong Democratic candidate, but a midterm electorate will be even more conservative than the presidential electorate that elected Heidi Heitkamp in North Dakota last week. Rating: Toss-Up
West Virginia: Jay Rockefeller is 77 years old. He may retire. If he does not, he will face a tough re-election. Joe Manchin has proved that West Virginia Democrats can still win statewide. Two polls have shown Rockefeller trailing Congresswoman Shelly Moore Capito. If Rockefeller runs, this is a toss-up. If not, call it Leaning Republican.
Safe Republican Incumbents: 12
Leaning Republican Incumbents: 1
Safe Democratic Incumbents: 8 (Retirements in Michigan or New Jersey would create toss-up races)
Strong Democratic Incumbents: 4
Leaning Republican Pick-Ups: 3
Toss-Up Democratic Seats: 4
Likely Republican Pick-Ups: 1
Looking at those numbers Republicans have a good chance at winning back a Senate majority. Maine is the only state where Democrats have any realistic chance to pick up a Republican-held seat, and that depends on Susan Collins retiring or losing a primary. Meanwhile, Democrats have to defend six seats in red states and six more seats in swing states. Retirements in Michigan and New Jersey would make things especially difficult. Right now, I would say that Republicans are narrow favorites to win back control of the Senate. This is very preliminary and we will know a lot more once candidates begin to announce their intentions. Strong recruiting from Republicans could easily make them heavy favorites to win the majority back.