Washington (CNN) – Democratic Rep. Joe Donnelly announced Monday morning that he's running for the U.S. Senate seat currently held by Republican Dick Lugar.
"I want to take the fight for American jobs and opportunities to the United States Senate. I want to make sure that the voices of hard working Hoosiers are heard in the U.S. Senate," Donnelly said in a video message to supporters.
In his announcement, the three-term lawmaker who represents Indiana's second congressional district located in the North Central part of the state, made a specific pitch to older voters.
"Our parents spent a lifetime paying into Social Security and Republican proposals to privatize it would leave Hoosier seniors vulnerable. They also want to privatize Medicare, which is plain wrong," Donnelly, attacking GOP proposals that Democrats claim will privative Medicare.
Monday's move was widely expected, after state lawmakers in Indiana re-drew Donnelly's current House district to include more Republican voters. Donnelly easily won reelection in 2008, but last November narrowly edged out his GOP challenger. Republicans won back two congressional seats and captured an open Senate seat in the midterm elections.
National Republicans immediately began comparing Donnelly to former Rep. Brad Ellsworth, the Democratic Senate nominee in Indiana last year. Ellsworth lost to former Sen. Dan Coats by double digits in the race to succeed retiring Democratic Sen. Evan Bayh.
"Just months after voters overwhelmingly rejected Brad Ellsworth's liberal policies, Joe Donnelly wants to sell Hoosiers on that exact same big-spending, job-killing Washington agenda. We welcome him into the race and look forward to him campaigning side-by-side with President Obama," National Republican Senatorial Committee Communications Director Brian Walsh said.
But Sen. Patty Murray, the chair of the Democratic Senatorial Campaign Committee, said with Donnelly in the race, her party has "a great pick up opportunity for Democrats next year."
"He is a strong candidate who knows how to beat the odds and win tough campaigns. Most importantly, Joe is exactly the kind of tireless fighter Indiana families need to rebuild the state's economy, create jobs and get Hoosiers back to work," Murray added.
As of now no other Democrats are considering a bid for the Senate nomination.
Lugar could face a very rough road to win his party's re-nomination. The six-term senator is facing a primary challenge from the right, from Indiana State Treasurer Richard Mourdock, who announced his bid on February 22.
While Lugar greatly outraised Mourdock in the first quarter of this year, he faces serious opposition from some local groups, like Hoosiers for a Conservative Senate, and some national organizations, like FreedomWorks. The groups are trying to find a consensus conservative candidate to take on Lugar in next year's GOP Senate primary.
Lugar, the most senior Republican member of the Senate, has been criticized by many Tea Party activists and other grass-roots conservatives for his willingness to work with Senate Democrats to seek bipartisan solutions, for his votes in favor of President Obama's Supreme Court nominees the past two years and for his 2008 vote in favor of the Troubled Asset Relief Program, better known as TARP. They were also upset with him for his early public openness last year to vote in favor of the New Strategic Arms Reduction Treaty (New START) with Russia.
The 79-year-old lawmaker was first elected to the Senate in 1976 after serving as mayor of Indianapolis. Lugar did not face a primary challenge in 2006 and won 87 percent of the vote in the general election, facing only a libertarian candidate.
– Follow Paul Steinhauser on Twitter: @PsteinhauserCNN