Democrat Suzanne Bonamici's victory in a special congressional election in Oregon on Tuesday night preserves the balance of power in the House.
Bonamici won the all-mail vote Tuesday by a double-digit margin over Republican Rob Cornilles to hold for the party the seat left vacant when David Wu resigned last summer amid allegations of sexual misconduct.
National Democrats made a sizable investment of cash and manpower in the contest, spending more than $1 million and making 336,000 phone calls and knocking on 148,000 doors in the 1st district.
House Minority Leader Nancy Pelosi called Bonamici's "a clear message from Oregon voters that they want their elected officials to create jobs and stand up for small business, while standing strong against Republican efforts to end the Medicare guarantee."
Democratic Campaign Committee chief Steve Israel said the party "held the Republican accountable for his extreme 'tea party' roots and his commitment to protecting the ultra wealthy at the expense of Medicare for seniors."
Republicans pointed out that the seat has never been in GOP hands and that Democrats will likely have to spend far more to win or hold seats on less friendly terrain.
When Bonamici is sworn in, it will return the Republican majority in the House to 50 seats -- 242 to 192, with one vacancy.
Voters in Arizona's 8th district will vote in a special primary election on April 17 and a general election on June 12 to fill the seat held until last week by Democrat Gabrielle Giffords.
There have been five special elections since the start of the 112th Congress, three won by Democrats. Each party has claimed a seat previously held by the opposite party.