Harkin is among a number of senators who have already announced they wonít be running again in 2014.
The primaries also clearly took their toll on more mainstream nominees such as former Wisconsin Gov. Tommy Thompson, who emerged from a Republican primary fight to the right underfunded and ill-prepared for the onslaught of Democratic ads that landed immediately on TV.
Democrats argue the top 2012 GOP recruits such as Thompson, former Montana Rep. Denny Rehberg and George Allen, a former governor and senator from Virginia, who all lost, were tied too closely to an unpopular GOP brand and the nationís capital.
ďBeing steeped in Washington and too branded in the D.C. brine is as much their problem as the rape comments,Ē Democratic Senatorial Campaign Committee spokesman Matt Canter said.
Still, Republicans like the look of the map as it stands today.