Suzanne Bonamici won Tuesday’s special election in Oregon’s 1st district, keeping the seat in Democratic hands.

The Associated Press called the race with Bonamici leading Republican Rob Cornilles 57 percent to 38 percent in the mail-only election. Ballots were due by 11 p.m. EST.

The Portland-area seat became vacant in August when Rep. David Wu (D) resigned after being accused of sexual assault. The district is solidly Democratic and has been represented by a Democrat for the past four decades, but the party took no chances after losing a New York seat in a special election last year.

The Democratic Congressional Campaign Committee spent $1.3 million in independent expenditures, mostly on TV ads that painted Cornilles as a tea-party-affiliated Republican, not the moderate he portrayed himself to be on the campaign trail.

Democratic-aligned House Majority Political Action Committee and EMILY’s List, which backs Democratic women who support abortion rights, invested an additional $500,000 total on the race, delivering an onslaught of ads against Cornilles that the Republican could not overcome.

The National Republican Congressional Committee expended $85,000 on a coordinated ad with Cornilles in mid-January following an internal Cornilles campaign poll showed the race within 4 points. Cornilles also received significant support from Speaker John Boehner (Ohio) and other Congressional Republicans, but in a district President Barack Obama carried in 2008 by 25 points, national Republicans could not find reason to invest heavily.

This is the first of three House vacancies created by scandal this cycle that was retained by the party that previously held the seat. Both parties lost a seat with the resignations of New York Reps. Chris Lee (R) and Anthony Weiner (D) in 2011.

In the two other previous special elections, Democrats held the seat of former Rep. Jane Harman (Calif.), and Republicans held the seat of now-Sen. Dean Heller (Nev.). There is at least one more special to go, as Democrats try to hold the seat of former Rep. Gabrielle Giffords (Ariz.).

Bonamici, a University of Oregon graduate, worked as a consumer protection attorney for the Federal Trade Commission and later worked in a private law practice. After a career break to raise her children, Bonamici took a job as a legislative assistant in the state House in 2001. She was elected to the state House in 2006, and was appointed and then elected to the state Senate in 2008 and 2010. She represented the 1st district’s population hub, Washington County, in both chambers.

Bonamici is married to federal Judge Michael Simon, who was confirmed by the Senate in June.

The 1st includes parts of five counties, stretching from Portland to the Pacific Ocean. Although it got slightly less Democratic after redistricting, the district changed little in shape and is not expected to be much more competitive for Republicans in November.

“Democrats successfully 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,” DCCC Chairman Steve Israel (N.Y.) said in a statement. “This election is a win for middle class Oregon families who want someone to fight for them.”