Although she lost her battle to unseat Sen. Susan Collins (R-Maine) last November, Democrat Chellie Pingree is still headed to Washington.

The 47-year-old former Maine Senate Majority Leader and small-business owner is slated to take over as the new president and chief executive officer of Common Cause, the public interest group that helped propel the recent passage of campaign finance reform legislation into law.

She replaces former Massachusetts Attorney General Scott Harshbarger, who stepped down last November and has returned to Boston to work for Mercer-Delta Consulting.

Pingree will actually begin her new job on March 7, when Common Cause holds its next board meeting, and said she is looking forward to helping the organization expand its membership and increase the group’s visibility.

“I think it’s a great time to strengthen the organization internally,” she said in an interview. “To increase the membership base, to work with the states … and to continue the agenda here in Washington.”

Pingree said her experience, both in the Maine Senate and on the campaign trail last year — she ended up with 42 percent of the vote — would help her in her new job.

“For me, it’s a great transition from being an elected official and running a great statewide campaign,” Pingree said, explaining that the grassroots support and volunteer network that helped her campaign is the same sort of grassroots activity from which Common Cause draws its strength and voice.

In her new position, Pingree will oversee all program activities, finances and communications for the group, which has more than 200,000 members and supporters nationwide.

Pingree is also looking forward to working on a variety of issues as Common Cause moves forward with its agenda in the 108th Congress.

“I was in the Legislature for eight years and worked on a lot of different kinds of legislation — corporate accountability, environmental, prescription drugs,” she explained. “It taught me a lot about working across the aisle to achieve successes on a whole variety of issues.”

This year, the group has a number of key items on its agenda, including reforming the Federal Election Commission and the system of public financing for presidential candidates. The group is also pushing for changes in the areas of corporate accountability and whistle-blower protection.

But Pingree emphasized that she will be working as much on the state level as she will on the federal level for Common Cause.

“Common Cause is active in so many states where real leadership is happening on campaign finance reform, and good government,” she said. “I’m looking forward to that association that Common Cause has in a lot of states.”

Before entering politics in the early 1990s, Pingree — who originally hails from Minnesota and is a 1976 graduate of the College of the Atlantic — spent many years as a farmer and running a national knitting products company.

Derek Bok, chairman of Common Cause, praised Pingree’s “outstanding record of bipartisan leadership and creative public policy in the Maine Legislature.”

“She has also demonstrated an ability to inspire people of all ages and persuasions to get involved in the Democratic process,” making her an “ideal choice to lead Common Cause at this stage in our history,” he said.