Former U.S. Senate candidate Chellie Pingree has been chosen president and chief executive officer of Common Cause, a nationwide watchdog group boasting a membership of 200,000.

“I don’t think I’ve ever been called ‘president’ before,” Pingree said Wednesday from her Washington office, calling the appointment “exciting and nerve-racking.”

In the selection process, Pingree was contacted by a search firm, she said, and competed with 100 candidates before winning the job Tuesday.

Since her unsuccessful campaign last fall for the seat held by Sen. Susan Collins, Pingree has been through a series of interviews for many “good job offers,” she said, and has spent some time relaxing.

Pingree, a Democrat and former state Senate majority leader, said she intends to remain active in Maine, noting she still has ties to state politics through her daughter, state Rep. Hannah Pingree, D-North Haven, who was elected to the Legislature last fall.

Chellie Pingree also plans to maintain her North Haven home and hopes “someday to run for office again.”

At Common Cause, Pingree, 47, will be paid $200,000 annually to oversee the work of some 85 full-time staff members in Washington and in 35 states, as well as its membership.

Pingree succeeds Scott Harshbarger, a Democrat and former Massachusetts attorney general who resigned as Common Cause’s leader last fall to join a consulting firm in Boston.

Common Cause was founded in 1970 by John W. Gardner, who had served in Lyndon Johnson’s Cabinet and who envisioned a movement propelled by focused, grass-roots activities reinforced with professional lobbying on Capitol Hill.

The nonpartisan group made an immediate impact, enlisting more than 100,000 members in its first year.

One of Common Cause’s early battles was fighting U.S. involvement in Vietnam.

The group also has pushed for campaign finance reform, civil rights, ethics, financial and lobbying disclosure and open meeting laws.

Pingree made the cost of prescription drugs the centerpiece of her Senate race.

Ironically, during Pingree’s bid for the U.S. Senate seat held by Collins, some of her campaign contributions were derived from so-called “soft money.” Soft money is money donated to a political party but not designated for a particular candidate. Parties can then use the money to evade federal limits on direct contributions to candidates.

Common Cause opposes such funding.

“No one understands better than a candidate how the campaign financing system needs to change,” Pingree said. She had opposed such practices before her Senate race, but decided to accept the money in her uphill 2002 race.

“They gave consideration to that,” Pingree said, referring to her new employer.

Pingree said she is a strong supporter of clean election laws and many of the initiatives for campaign funding reforms, such as one that would provide free media time for candidates.

In her new role, Pingree will work with other states in instituting clean election laws and corporate accountability. Pingree likes the idea that she will continue to be involved in many of the same issues she dealt with in elective politics, such as health care and prescription drug issues, she said.

Other responsibilities will be to oversee all program activities, finances and communications for the organization.

When citizens need a voice, Common Cause can help them become involved, she said, adding that with so much cynicism about government, “Common Cause is kind of more important than it ever was.”

From 1992 to 2000, Pingree served in the Maine Senate, where she spent the last four years as majority leader. She was prohibited from seeking re-election because of term limits.