PORTLAND, Ore. -- Determined not to lose another friendly district because of a sex scandal, Democrats and their allies have pumped more than $1 million into an Oregon special election race that has turned into a vicious exchange of attacks over the airwaves.

Voters are deciding who should replace former Rep. David Wu, a seven-term Democrat who resigned last year following a string of bizarre news stories that began with photos of the congressman wearing a tiger costume and ended with a young woman's accusation that he made an unwanted sexual advance.

Voters have until 8 p.m. Tuesday to return their ballots in the all-mail election.

Republican Rob Cornilles, a sports business consultant, has tried hard to extend the scandal that brought down Wu to the Democrat who wants to take his place, former state Sen. Suzanne Bonamici. She says the race is about the future, not about Wu.

Bonamici and independent groups that support her have gone after Cornilles for missing tax payments for his business and for inconsistent statements about the number of jobs his company has created.

Oregon's 1st Congressional District is the state's economic engine, encompassing downtown Portland and the fast-growing western suburbs that are home to the Silicon Forest high-tech hub and the global headquarters for athletic-wear giants Nike Inc. and Columbia Sportswear Company. It stretches across agricultural communities to the Pacific coast. Democrats have represented the district since 1975, and its voters overwhelmingly supported President Barack Obama.

But Democrats do not want to see a repeat of what happened last year in a heavily Democratic New York district, when a Republican won a special election after Rep. Anthony Weiner acknowledged sending provocative text messages and resigned.

The Democratic Congressional Campaign Committee has spent $1.3 million to boost Bonamici. Political committees for a union, abortion-rights groups and a super PAC allied with Democrats have also chipped in with their own mail or television ads.

Democrats insist they're not scared. They've likened their investment to an insurance policy to avoid any doubts about the party's strength that would inevitably follow a loss in a liberal state like Oregon. The National Republican Congressional Committee has spent just $85,000 on the race.

Cornilles, 47, is making his second bid for the seat after losing to Wu in 2010. He's centered his pitch on his experience running a sports-marketing firm, hoping to swing an upset with a relentless focus on jobs and a run toward the center. Unemployment in the Portland area dropped to 7.8 percent in November 2011, according to the Bureau of Labor Statistics.

Bonamici, 57, is mixing traditional Democratic themes of protecting Social Security and Medicare with a pledge to tackle the national debt by getting Washington's priorities in order.

Without reliable public polling it's anyone's guess how close the race will be.

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