Former Secretary of State Matthew Dunlap has filed the necessary paperwork to challenge U.S. Sen. Olympia Snowe in the 2012 election.

In a filing with the Federal Election Commission dated Oct. 31, the Old Town Democrat registered Dunlap For Senate as an official campaign committee.

Dunlap, Maine’s secretary of state until earlier this year, has been rumored as a challenger to Snowe for many months but hadn’t made up his mind as of this summer.

He confirmed Wednesday that he filed the paperwork and said he would talk more about his plans when he makes a formal announcement in the coming days.

Another Democrat, State Rep. Jon Hinck of Portland, has filed the same paperwork but has not made a formal announcement about his plans. Sean Flaherty, Hinck’s campaign manager, said Wednesday that Hinck would go public soon as well.

“We look forward to a potential Democratic primary for the U.S. Senate next year,” Flaherty said. “Primaries are great for the democratic process and help to energize the electorate. Moreover, it’s time for an incumbent who has spent 33 years in Washington to go.”

Snowe, a three-term senator and former eight-term U.S. House member, already faces a primary challenge next June from two candidates, Scott D’Amboise and Andrew Ian Dodge, both tea party-backed conservatives.

Earlier this year, Dunlap, 47, served as interim director of the Sportsman’s Alliance of Maine after longtime director George Smith stepped down. Dunlap served four terms in the Maine House from 1996-2004 before he was chosen as secretary of state. He has bachelor’s and master’s degrees from the University of Maine.

Hinck, a lawyer from Portland, is serving is third term in the Maine House. For about a decade, Hinck worked for the environmental group Greenpeace USA and later worked for the Natural Resources Council of Maine.

At this point, Snowe is still viewed by most as a heavy favorite. Since 1978, she has never lost an election and in 2006, she was reelected to the Senate with 74 percent of the vote.

Sandy Maisel, director of the Goldfarb Center for Public Affairs and Civic Engagement at Colby College, called Snowe is the most popular Maine politician he has seen in 40 years.

Christian Potholm, professor of government at Bowdoin College, said he doesn’t know of any candidate, Republican or Democrat, that could seriously challenge Snowe.

“She’s a warrior,” Potholm said. “She’s not going to roll over because of some tea party candidate or some upstart Democrat.”

A recent survey conducted by Public Policy Polling out of North Carolina revealed that Snowe was favored by 62 percent of Republicans polled, compared to 10 percent for D’Amboise and 7 percent for Dodge.

Justin Brasell, Snowe’s campaign manager, said the senator looks forward to campaigning on her many accomplishments on behalf of Maine workers.