Former Virginia Gov. Mark Warner’s (D) YouTube announcement Thursday morning that he will seek the seat that is being vacated by retiring Sen. John Warner (R) in 2008 instantly has transformed the Old Dominion into a key Senate battleground next year.

In his announcement, which was posted on his new Senate campaign Web site, Mark Warner said, “I’ve decided the way I can contribute most to getting our country back on the right track is to serve in the United States Senate. So after this November’s legislative elections I will announce a formal candidacy for the Senate and I’m going to work like heck for the next 14 months to get Virginians to hire me.”

Warner, who also had been mulling another gubernatorial run in 2009, is considered a dream candidate by Democrats.

John Warner’s retirement also has set up an all-but-certain battle for the GOP nomination between Rep. Tom Davis, a social moderate, and former Gov. Jim Gilmore, an anti-tax conservative. State Republicans say they are bracing for a nasty nomination fight.

In his announcement, Mark Warner touted his record as governor from 2001 to 2005 and also took a shot at the state of the Commonwealth’s government when Gilmore left office.

“Six years ago I think it was clear to most Virginians that we needed a change of directions in the Commonwealth,” Warner said. “Virginia was mired in fiscal crisis, we weren’t investing in our future and partisan politics was bringing Richmond to a grinding halt. Virginians were ready for change in 2001 and I was honored to be elected governor. We brought folks together, focused on getting results and together we accomplished some great things. … I’ll try to bring the same practical problem solving approach we used in Virginia to Washington.”