Johnsonís decision not to seek re-election will make 2014 a harder slog for the Democratic Party.
On the surface, the numbers are harrowing for Democrats, who have a limited number of offensive opportunities and must defend 21 of the 35 seats ó including special elections ó up this cycle. That includes seven states Obama lost and a total of at least nine potentially competitive, Democratic-held seats.
South Dakota and West Virginia are no doubt two of the best pickup opportunities for Republicans, who already have top recruits in place. Former South Dakota Gov. Mike Rounds and West Virginia Rep. Shelley Moore Capito announced their bids shortly after the elections in November.
While still recruiting in West Virginia, Democrats already have potential candidates in South Dakota in former Rep. Stephanie Herseth Sandlin and U.S. Attorney Brendan Johnson, the senatorís son.
Johnson said during his retirement announcement that it was no secret he had spoken with his son about running for Senate. But later, in a news conference, Johnson noted that he has no plans to be active during the race and is busy enough with his duties in the Senate.
In Iowa, Democratic Rep. Bruce Braley immediately announced his candidacy after Harkin retired. Democrats like their chances in the Hawkeye State should GOP Rep. Steve King, a conservative who top Republican strategists worry is too undisciplined to win statewide, decides to run. King told CQ Roll Call recently that he is still undecided.
The Democratsí most vulnerable incumbents are, at this point in the cycle, at least an even bet for re-election. Many of them ó including Alaskaís Mark Begich, North Carolinaís Kay Hagan, Louisianaís Mary L. Landrieu and Arkansasí Mark Pryor ó are still awaiting major GOP challengers.
Along with Capito and Rounds, Republicans also have candidates to take on Democratic Sen. Max Baucus of Montana, including former state Sen. Corey Stapleton.
Democratsí optimism stems in part from the GOPís recent track record of nominating weak general election challengers. In 2012, top Senate GOP recruits ran lackluster campaigns. Whatís more, in the past two cycles, a handful of long-shot conservatives proved unable to adequately compete for a general electorate.
A total of seven senators, including five Democrats, have announced their retirements so far this year, including Johnson, Harkin and Rockefeller. The remaining four are Democratic Sens. Carl Levin of Michigan and Frank R. Lautenberg of New Jersey and Republican Sens. Saxby Chambliss of Georgia and Mike Johanns of Nebraska.
Given those four statesí recent electoral trends, both parties start out favored to hold their own open seats. But the Levin and Chambliss seats could eventually become more competitive based on whom the parties recruit and which candidates make it out of what are likely to be crowded GOP primaries.