Johanns’s retirement likely won’t give Democrats much of an opportunity for a pick up in the deeply Republican state. Republican Sen. Deb Fischer easily defeated former Democratic Sen. Bob Kerrey last year, winning nearly 60 percent of the vote.

“The Cornhusker state will look to continue its strong conservative tradition by electing an equally dedicated Republican leader in 2014,” National Republican Senatorial Committee chairman Jerry Moran said in a statement.

The leading candidate to succeed Johanns is current Republican Gov. Dave Heineman, according to a senior Republican operative. Heineman, who has served two full terms since 2005, as Nebraska’s governor, is term-limited from running again in 2014.