PORTLAND, Ore. - Democrats will hold onto an Oregon congressional seat left vacant when David Wu resigned in a sex scandal.

Democrat Suzanne Bonamici defeated Republican Rob Cornilles Tuesday night. With 69 per cent of the vote counted, Bonamici led Cornilles 54 per cent to 39 per cent.

National Democrats poured more than $1 million into the Portland-area district, determined not to drop another safe seat after losing a New York district left vacant by Anthony Weiner, who acknowledged sending provocative text messages and resigned.

The Taiwan-born Wu, the first Chinese-American to serve in Congress, stepped down from his House seat in August after a newspaper reported that the 18-year-old daughter of a campaign donor accused the seven-term Democrat of making an unwanted sexual advance at a Thanksgiving holiday dinner. His resignation capped months of reports about Wu's bizarre behaviour that included widely-panned photos of the congressman wearing a tiger costume.

Bonamici, a former state senator who gave up her seat to run for Congress, emphasized her experience in the legislature and as a lawyer working on consumer protection issues at the Federal Trade Commission. She talked about controlling the national debt, but stuck mostly to traditional Democratic themes like preventing cuts to retirement benefits and health care programs for the elderly.

Cornilles, owner of a consulting firm that does business with sports franchises, promoted his business experience. But he faced an uphill climb in a district where Democrats outnumber Republicans and President Barack Obama enjoyed significant support in the 2008 campaign.

Democrats and their allies pummeled him with television ads that attacked his business credentials and tried to align him with the conservative tea party movement.