As the latest sign that Democrats are fretting their fate in a friendly district where they should have no trouble winning, Republicans pointed to House Majority PAC's decision to join the air wars in support of Bonamaci. Cornilles campaign manager Mary Anne Ostrom said the campaign's media buyer had informed them that the liberal PAC was spending more than $200,000 to buy airtime in the Portland area.

A spokesman for House Majority PAC confirmed that it would start airing ads against Cornilles on Thursday, but declined to provide the size of the buy. The PAC said the ads would target "Cornilles's dishonest jobs record" and would cite a recent article questioning Cornilles's job-creation claims and a tax lien that was briefly placed on his business.

Voting is already under way in the all-mail-in special election to replace Wu, who resigned in July amid a sex scandal, and will continue until Jan. 31.

The survey by Republican pollster Bob Moore was conducted Jan. 11-12 using live telephone interviews and had a margin of error of 6 percentage points. The poll's sample of 300 likely voters included 40 percent registered Democrats, 35 percent Republicans and 25 percent unaffiliated or Independent voters.