Republican Rep. Shelley Moore Capito of West Virginia will announce a bid for the Senate on Monday, taking aim at Democratic Sen. Jay Rockefeller, Roll Call has confirmed.

Rockefeller, 75, and a West Virginia institution first elected to the Senate in 1984, is considered a top potential Senate retirement.

Capito, first elected in 2000, has long been considered the Republicans’ top prospect to take a Senate seat in the Mountain State. But she took a pass on running against Democratic Sen. Joe Manchin III this year. A popular former governor, Manchin cruised to victory earlier this month. She also passed on challenging Manchin in the 2010 special election to fill the vacancy caused by the death of Democratic Sen. Robert C. Byrd.

Capito’s announcement means the 2nd District seat she currently represents will become open.

National Democrats on Sunday night were already eyeing the seat.

“Game on,” a national Democratic operative emailed.

The news of Capito’s announcement was first reported by the West Virginia MetroNews on Sunday night and confirmed by a GOP source.