(Corrects election to 2012 from 2010 in 2nd paragraph)
* Democratic senator faced potentially tough campaign
* West Virginia voters leaning more Republican
By Richard Cowan
WASHINGTON, Jan 11 (Reuters) - Democratic Senator Jay Rockefeller announced on Friday that he will not seek a sixth term in 2014 to represent his home state of West Virginia, which has been trending more Republican in recent years.
President Barack Obama, a Democrat, failed to win West Virginia in either of his two races in 2008 and 2012. Rockefeller, 75, could have faced a spirited race next year, especially if Republican Representative Shelley Moore Capito decided to challenge him, as expected.
"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 said in Charleston, West Virginia.
Rockefeller currently serves as chairman of the Senate Commerce, Science and Transportation Committee, which has broad oversight powers, including the aviation and communications industries, consumer protection and rail and highway programs.
The liberal Democrat, whose full name is John D. Rockefeller IV, is the great-grandson of the famous oil tycoon who became a billionaire in the late 1800s.
Senator Rockefeller has been a strong supporter of organized labor and was an active participant in healthcare reform initiatives, including Obama's successful effort in 2010.
The healthcare reform law, which Republicans deride as "Obamacare," has not been strongly embraced by voters, although some of its major provisions will not take effect until 2014.
Nathan Gonzales, deputy editor of the Rothenberg Political Report, said Rockefeller's retirement could complicate Democrats' efforts to keep control of the Senate in 2014.
Gonzales added that West Virginia voters increasingly have become uncomfortable with the Democratic Party on hot-button issues such as gun control, gay marriage and abortion.
"There is a cultural tension between West Virginia and the national Democratic Party," after years of Democratic strength in the coal-producing state, Gonzales said.
In 2014, Democrats will try to defend 20 Senate seats, while Republicans have 13 up for grabs. Currently, Democrats hold a 55-45 edge in the Senate when including Bernie Sanders of Vermont, an independent who often aligns himself with Democrats.
Rockefeller also has been a protector of West Virginia's coal industry, an important economic force in his impoverished state. In 2009 and 2010, Rockefeller urged the Senate to take a careful approach to climate change legislation that would have aimed to reduce the use of carbon-emitting fossil fuels, such as coal, over the long-term.
Instead, Rockefeller promoted a system that would have permanently stored carbon dioxide industrial emissions underground - a commercially unproven technology.
That legislative effort ultimately sputtered in the Senate.
When Democratic Senator Joe Manchin ran to replace the late Senator Robert Byrd, a towering political figure in the state, Manchin ran a campaign video ad showing the candidate taking aim with a rifle at the "cap and trade" climate bill. The ad resonated with West Virginia voters.
The Rockefeller name, long associated with vast wealth in America, also represented a political dynasty.
Senator Rockefeller's uncle, Nelson Rockefeller, was a moderate Republican who served as governor of New York and vice president under President Gerald Ford. Another uncle, Winthrop, was governor of Arkansas, a rural state with deep pockets of poverty, like West Virginia, where Senator Rockefeller served as governor before coming to Washington.
It was unclear what Democratic candidates might emerge in the race for Rockefeller's seat.
One name that could stand out is West Virginia Secretary of State Natalie Tennant, Gonzales said.
(Editing by Vicki Allen)