Tsongas, the widow of former Sen. Paul Tsongas (D-Mass.), has declared victory and could be sworn into the seat her husband once held as early as Wednesday.

Democratic Congressional Campaign Committee Chairman Chris Van Hollen (D-Md.) congratulated Tsongas on her win.

“She is a lifelong advocate for children and working families in Massachusetts,” Van Hollen said. “Niki will be a tremendous asset to the Democratic caucus. Massachusetts voters sent a clear message: They support candidates who fight for their values to provide children’s health care and work to end the war in Iraq.” 

Van Hollen’s Republican counterpart praised the close results in the Democratic-leaning district as a sign of things to come.

“Tonight, Jim Ogonowski sent a message to the Washington establishment and the Democratic Party that will reverberate throughout next year’s election. Democrats have officially forfeited the mantle of change," said National Republican Congressional Committee Chairman Tom Cole (R-Okla.). “Jim’s hard-fought, grassroots campaign exposed a shift in the political tide, and most impressively, he did it in the bluest of blue states.”