West Virginia Democratic Sen. Jay Rockefeller's decision not to run for a sixth term is boon to Republican chances of picking up a seat that hasn't been in GOP hands since the 1950s, because it removes a well-known incumbent from a race in which a strong Republican candidate is already in the running, all in a state with an overall tilt that presents the GOP with opportunity.

(J. Scott Applewhite/AP)

Rep. Shelley Moore Capito (R) announced her decision to run late last year, giving Republicans a competitive chance in the race, even if Rockefeller had decided to run. Capito comes from a well-known political family, and Republican strategists have been hopeful she would run for some time.

Without Rockefeller, Democrats must fill the gap left by a well-known pol with a famous last name and the advantages of incumbency. Rockefeller, 75, was first elected to the Senate in 1984 in a competitive race. Since then, he's won reelection with at least 60 percent of the vote. In 2008, he carried 64 percent of the vote en route to a fifth term.

The state of play in West Virginia makes an already tough 2014 Senate map for Democrats even more challenging. With more Democrats than Republicans defending seats, and a large number of red or swing state Democrats set to face voters, Republicans have a chance to make gains. Counting Independents who caucus with the Democrats, the party has a 55-45 advantage in the Senate right now.

While it's been a long time since West Virginia has sent a Republican to the Senate and Democrats have a strong registration advantage in the state, West Virginia's been tilting heavily Republican at the presidential level. Mitt Romney carried the state by about 17 27 points in 2012.

The state's junior senator, Democrat Joe Manchin, has retained his popularity by carefully sticking to a moderate profile in the Senate and bucking the Obama Administration on energy issues. Two of the state's three House members are Republicans.

"Senator Rockefeller’s decision not to seek reelection makes West Virginia an even stronger pickup opportunity for Republicans in 2014," said National Republican Senatorial Committee Executive Director Rob Collins in a statement.

Republican strategists have been bullish about Capito -- whose father, Republican Arch Moore, beat Rockefeller in the 1972 governor’s race, before losing to him in 1980 -- for some time. While a pair of conservative groups expressed displeasure at her record on spending, neither group could name a more conservative candidate they would like to see run against her.

Rep. David McKinley (R) is not ruling out his own Senate run, though he says he likes what he is seeing from Capito.

For Democrats, the challenge is now to find a recruit that can match Capito's name ID and congressional resume. Rockefeller's decision shouldn't come as a major surprise to his party; the senator stoked chatter about his possible retirement in the summer of 2012 with a speech in which he offered tough talk for the coal industry, a dominant force in West Virginia.

The crowded 2011 Democratic gubernatorial primary may offer hints about which Democrats are likely to take the plunge in the Senate race. The runners up to current Gov. Earl Ray Tomblin include Secretary of State Natalie Tennant, state House Speaker Rick Thompson, and state Treasurer John Perdue, among others. The state's only Democrat in the House delegation Rep. Nick Rahall, is another possibility, as is former senator Carte Goodwin, who served for a brief stint in 2010.

Rockefeller's decision to bow out early gives Democrats time to find suitable candidates to take his place. It's much better for his party that he do this now, and not 6-12 months down the road.

"I am confident we can elect an independent-minded Democrat to [Rockefeller's] seat next November," said Democratic Senatorial Campaign Committee Chairman Michael Bennet (Co.) in a statement. "Democrats maintain nearly a two to one voter registration advantage over Republicans in West Virginia and I know there are a number of leaders there who will consider taking this next step to serve their state."

But make no mistake: The GOP is licking its chops at the prospect of picking up West Virginia. And Democrats will face a real challenge holding the seat.