Sen. Carl Levin, D-Mich., announced today that he will not seek reelection next year, a decision that presents Republicans with a strong opportunity to pick up a seat in the 2014 midterms.

“I have decided not to run for re-election in 2014,” Levin announced today. “As Barbara and I struggled with the question of whether I should run again, we focused on our belief that our country is at a crossroads that will determine our economic health and security for decades to come.  We decided that I can best serve my state and nation by concentrating in the next two years on the challenging issues before us that I am in a position to help address; in other words, by doing my job without the distraction of campaigning for re-election.”

Levin is practically unbeatable, but his retirement could expose the weakness of the Michigan Democratic bench and give the state Republicans a strong shot to take the seat — especially when you don’t have a presidential election machine driving turnout for Democrats.

Republicans hold every statewide constitutional office. Gov. Rick Snyder, R-Mich., won in 2010, as did Secretary of State Ruth Johnson and Attorney General Bill Schuette. The victories weren’t mere Tea Party wave flukes, either. The previous two secretaries of state were Republicans, as was Schuette’s predecessor, Mike Cox.

Lt. Gov. Brian Calley, R-Mich., is a West Michigan conservative with a statewide profile, because of his office, who might have some appeal in the moderate southeast Michigan counties that propelled Snyder to victory in the 2010 primary. He could also run on Snyder’s very solid economic record — the state unemployment rate has dropped from 11 percent to 8.9 percent, while Fitch has upgraded the state’s bond outlook — although his nomination might mobilize unions angry about the passage of right-to-work in the state.

As for the Democrats, they nominated the mayor of Lansing to oppose Snyder in 2010. Virg Bernero lost the general election, garnering just 40 percent of the vote.

State Sen. Gretchen Whitmer, D-East Lansing, was floated as a Democratic challenger to Snyder, but she turned it down. “To be the kind of Mom I want to be for my girls simply does not allow me to make the kind of commitment necessary to run a successful campaign for Governor at this point in their lives,” Whitmer wrote in an email to supporters.

Former Rep. Mark Schauer could be an interesting choice. He lost in 2010 in a swing district that had he won in the previous wave election of 2008. Republicans drew him out of the district. He never had a statewide profile, though, unlike some of the Republican possibilities.

The state Democratic Party’s strongest candidate might be former Gov. Jennifer Granholm, D-Mich. She won reelection in 2006, but that was a terrible year for Republicans and she was able to blame the state’s economic woes on President Bush and the national climate.

Also, she might have damaged her brand with an outlandish performance at the Democratic National Convention last year — her Howard Dean-esque delivery looked very different from the Granholm Michigan voters knew as governor.