CONCORD, Mass. (AP) — Another candidate has entered the crowded Democratic field in the state's third congressional district.

Former U.S. Ambassador to Denmark Rufus Gifford announced on Monday that he will seek the seat held by Democrat Niki Tsongas, who plans to retire at the end of her current term.

The 43-year-old Gifford is a Concord resident. He was named to the diplomatic post in 2013 after serving as a top fundraiser for then-President Barack Obama's 2012 re-election campaign.

Gifford is the seventh Democrat to join the race with others considering a run.

Two Republicans have also announced a run for the seat.

Tsongas, the widow of former U.S. Sen. Paul Tsongas, has served in the House since 2007.