Updated 12:20 p.m. -- Democrat Sen. Jay Rockefeller will not seek a sixth term in 2014, giving Republicans a chance to pick up a Senate seat next cycle.
The news comes after Republican Rep. Shelley Moore Capito said that she would seek Rockefeller's seat.
Rockefeller, 75, held a press conference to announce his decision this morning.
A descendent of famed oil baron John D. Rockefeller, the West Virginia lawmaker's family legacy is rich with politics; New York Gov. Nelson Rockefeller and Arkansas Gov. Winthrop Rockefeller were his uncles.
Rockefeller moved to West Virginia in the 1960s. He held the governorship for eight years before winning election to the Senate in 1984.
He easily won his last race in 2008, defeating his GOP opponent by a 64%-36% margin. But given West Virginia's more conservative tilt -- at least in presidential elections -- winning re-election in 2014 would have been far from guaranteed.
The National Republican Senatorial Committee said in a statement that Rockefeller's departure represents "a strong pickup opportunity" in 2014.
"Voters next year will have a clear choice between a Democrat who will be a loyal vote for President Obama and Harry Reid as they try to kill West Virginia’s coal industry and bankrupt our country with reckless government spending, versus a Republican who will serve as an effective check-and-balance on their liberal agenda and work to get our country’s economy back on track," NRSC executive director Rob Collins wrote.
NBC's Carrie Dann contributed to this report.