SOUTH BEND, Ind. (AP) — Democratic Rep. Joe Donnelly announced Monday he was jumping into the race for the Indiana seat in the U.S. Senate currently held by Republican Richard Lugar.

The three-term congressman from South Bend made the announcement in a video posted to his campaign website. Donnelly is entering a race where Democrats see potential for winning because of the strong challenge Lugar is facing from his right by state Treasurer Richard Mourdock for the Republican nomination.

Donnelly doesn’t mention either Lugar or Mourdock in the 21/2-minute announcement video, although he does speak against what he called Republican proposals to privatize Social Security and Medicare.

Much of the announcement is biographical and seems to anticipate a 2012 campaign focusing on the economy.

“I want to take the fight for American jobs and opportunity to the United States Senate,” Donnelly said.

By entering the race, Donnelly — who had also weighed a run for governor or running again for his congressional seat — gives national Democrats a recruiting victory. Party activists believe the Indiana Senate seat will be a strong pickup opportunity if Lugar does not win his primary, though Republicans believe the seat that Lugar has held since 1977 will remain firmly in their grasp regardless.

National Republican Senatorial Committee issued a statement comparing Donnelly to former Rep. Brad Ellsworth, another moderate Democrat who lost badly to GOP Sen. Dan Coats in last year’s Indiana Senate race.

“Just like Ellsworth, Donnelly has been a partisan rubber stamp for liberal Democrat leaders in Washington,” said Brian Walsh, a spokesman for the Republican Senate committee.

Elected to Congress in 2006, Donnelly cruised to re-election in 2008 but escaped with a narrow victory in 2010 over Republican Jackie Walorski, a favorite of tea party activists.

Donnelly began talking about running for the Senate or governor several months ago with the expectation that the Republican-controlled Legislature would move more GOP areas into his northern Indiana congressional district — as it did under the redistricting plan that was approved last month.

Donnelly voted in favor of President Barack Obama’s signature health care plan, but spent much of his 2010 campaign seeking to distance himself from national Democrats.

In one ad, he referred derisively to the “Washington crowd” as an image of then-Speaker Nancy Pelosi and Obama flashed on the screen. Donnelly supports handgun rights and has previously won the support of the National Rifle Association in his races.