Popular former Virginia Gov. Mark Warner formally announced today that he is running for the U.S. Senate seat being vacated by Republican Sen. John Warner. The announcement immediately give the Democrats a strong frontrunner in a race that would help solidify a Democratic majority in the U.S. Senate, and makes the possibility of two Democrats representing the Commonwealth of Virginia for the first time since 1970 highly likely.

No other serious Democrat is likely to challenge Warner, who left office as one of the most popular governors in Virginia history after serving only one term. Republican challengers are likely to include Rep. Tom Davis or former governor Jim Gilmore, and of course, possibly “Pitchfork” Pat Buchanan.

Could Davis pose a serious threat to Warner? Matt Yglesias points to a Rasmussen Poll to say probably not:

In a match-up of former Virginia Governors, a Rasmussen Reports telephone survey finds Warner leading Jim Gilmore by twenty percentage points, 54% to 34%. Warner also starts the season with a comfortable lead over Virginia Congressman Tom Davis. The Rasmussen Reports poll shows Warner attracting 57% of the vote while Davis earns 30%.

This announcement only makes us more desperate for Buchanan to jump into the race, if only to give us something to write about. As last year’s Allen vs. Webb campaign taught us, anything can happen the course of a Senate campaign in Virginia, but it’s hard to imagine anyone giving Mark Warner a serious challenge at this point.