[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/08/27/art.melancon0827.cnn.jpg caption="Melancon officially entered the race in a Web video released Thursday."]
(CNN) - In a highly-expected move, Democratic Rep. Charlie Melancon said Thursday that he will enter the race to take on Republican Sen. David Vitter in the Louisiana Senate race next year.
"Today, I'm announcing my candidacy for the U.S. Senate to replace David Vitter, because Louisiana deserves better," said the three-term congressman in a video message sent to supporters.
Vitter has been focusing his fire on Melancon for months, including a Web ad earlier this summer that took a swipe at the congressman for fundraising in the Northeast, and attempted to tie him to President Obama.
"It didn't take long for President Obama and his liberal friends to throw their support behind David's opponent, Charlie Melancon," said the incumbent in a fundraising appeal to his own supporters, slamming Melancon for "(flying) up to Martha's Vinyard to collect campaign cash from Obama's wealthiest supporters at cocktail parties in Massachusetts."
Melancon - a fiscally conservative Blue Dog Democrat who has publicly opposed some of the main elements of the president's health care proposal, and is considered a potential swing vote on a final bill - has been a prime target on the issue this summer for groups on both sides of the debate.
FreedomWorks, one of the most active conservative organizations opposing President Obama's health care reform plan, had him on its shortlist of town hall targets heading into the August recess. On the other side of the spectrum, the congressman was pressured to back the Obama plan in ads from Organizing for America, the president's campaign arm at the Democratic National Committee, and Health Care for America Now, the coalition of union and other liberal groups that has provided the major third-party support for the proposal.
Vitter, who weathered a very public prostitution scandal earlier in his term, is currently considered to have the edge over any potential Democratic opponent, including Melancon - who won last cycle in a district where six in 10 voters supported John McCain, a fact which may turn his former seat into a likely GOP pickup. In the first half of the year, the Democrat built up a $1.2 million warchest to take on Vitter in 2010.
UPDATE: Within minutes of Melancon's announcement, the National Republican Senatorial Committee released a new Web video tying Melancon to Obama and House Speaker Nancy Pelosi.