Sen. Jay Rockefeller, the five-term West Virginia Democrat who has spent more than four decades in public life, announced this morning that he will not run for re-election in 2014.

Speculation about Rockefeller's possible retirement has grown since last summer, when he made a series of statements and speeches taking on his state's most powerful industry -- coal. He accused companies of failing to modernize and using scare tactics.

"As I approach 50 years of public service in West Virginia, I've decided that 2014 will be the right moment for me to find new ways to fight for the causes I believe in and to spend more time with my incredible family," Rockefeller, the chairman of the Senate Commerce, Science and Transportation Committee, said today.

During a speech this morning at the Culture Center in the state capital of Charleston, Rockefeller, 75, highlighted his accomplishments, including an ongoing fight for coal miner safety.

"I pressed to make coal mining safer. To resolve black lung cases quicker," he said, recalling the time when he threatened to push the Senate into working during Christmas in support of the 1992 Coal Act, which preserved health benefits for retired miners.

Conservatives have criticized Rockefeller for his support of President Obama and Obama's landmark health care reform law. Rockefeller said today, "I know it's not particularly popular in West Virginia, but frankly, that's OK."

Reacting to Rockefeller's decision, 19-term West Virginia Rep. Nick Rahall (D) said in a statement, "We have fought many battles together, miners' safety, health care, countless economic development initiatives and road projects. Through it all, Jay has been tireless in his work and his dedication never as much as flickered."

Even before Rockefeller's announcement today, Republicans had seen the state as a major target in 2014.

Today Rob Collins, executive director of the National Republican Senatorial Committee, said, "Sen. Rockefeller's decision not to seek re-election makes West Virginia an even stronger pickup opportunity for Republicans in 2014."

Six-term Rep. Shelley Moore Capito (R-W.Va.) announced in November that she would run for the seat, signaling that she would be conducting a robust pro-coal campaign (Greenwire, Nov. 26, 2012).

West Virginia University political science professor Neil Berch said the announcement "certainly makes Shelly Moore Capito the front-runner for the seat."

A West Virginia poll conducted by R.L. Repass and Partners Inc. last year showed Capito, the daughter of former West Virginia Gov. Arch Moore (R), leading Rockefeller 48 percent to 44 percent in a hypothetical matchup, with 8 percent of respondents undecided.

But Capito is likely to face a challenge from the right in the Republican primary.

Chris Chocola, president of the conservative Club for Growth, responded to her announcement by calling her an establishment candidate. He said, "Congresswoman Capito has a long record of support of bailouts, pork and bigger government." In a move that some analysts attributed to an attempt to protect her right flank, Capito on New Year's Eve voted against the deal to avert the so-called fiscal cliff.

Matt Hoskins, executive director of the Senate Conservatives Fund, the group associated with former Sen. Jim DeMint (R-S.C.), today also called for a more conservative choice.

"Now that Rockefeller has taken himself out of the race, the door is wide open for Republicans in West Virginia to nominate a true conservative," he said. "President Obama lost the state by 26 points, so there's no reason a courageous conservative can't win this race."

Earlier this week, Rep. David McKinley (R-W.Va.), who just won re-election for his second term and is a big champion of coal, did not rule out a run against Capito during an interview with West Virginia MetroNews.

"I am watching to see what happens with Shelley, how well she continues to maintain a fiscal policy that is good for this country," said McKinley.

This morning, West Virginia GOP Chairman Conrad Lucas, also on MetroNews, called Capito and McKinley "two very strong voices" in Congress for state Republicans. And he argued that the state is trending in the Republicans' direction.

"West Virginia is not the state that [it] was when Rockefeller first moved here to run for office," he said, instead predicting a tough primary fight on the left. "We know the Democrats are going to have a circular firing squad."

Although Democratic presidential nominees have fared poorly in West Virginia since 2000, Democrats continue to dominate most statewide offices and the state Legislature.

Several Democrats have surfaced as possible contenders for Rockefeller's seat, including Secretary of State Natalie Tennant; state House Speaker Rick Thompson; and former Sen. Carte Goodwin, who served in the Senate for several months in 2010 after the death of long-term Sen. Robert Byrd (D-W.Va.). Rahall, whose re-elections have become increasingly difficult, is also said to be considering a run.

West Virginia Democratic Party Chairman Larry Puccio said he doesn't expect a contentious fight for his party's nomination. "I really don't. There's a lot of wishful thinking. But I don't think there's a lot of scramble," he said this morning.

Noting Democrats' continued electoral success in local West Virginia races, Puccio said, "The right candidate who runs a good campaign has every opportunity in the world of serving West Virginia."

Rockefeller's retirement could also set off a scramble to replace him as the top Democrat on the Commerce Committee. Sen. John Kerry (D-Mass.) is the next most senior Democrat on the panel, but he is expected to be confirmed as secretary of State shortly. Sen. Barbara Boxer (D-Calif.) is next, but she is currently chairwoman of the Environment and Public Works Committee. If she chooses to keep that job, Sen. Bill Nelson (D-Fla.) would be the next in line.

Rockefeller first arrived in West Virginia as a VISTA volunteer in 1964. He went on to serve stints in the West Virginia House of Delegates, as secretary of State, as president of West Virginia Wesleyan College, as governor and finally as senator.

Rockefeller said today that he intends to finish his term, predicting tough battles ahead, including on deficit reduction.

"Really, really rough. And I want to be part of that fight," Rockefeller said, talking about his intensity when fighting for the state. "Let me say clearly that I have every intention of keeping up this intensity."