The Democrat led GOP businessman Rob Cornilles 52 percent to 41 percent in a poll paid for by the liberal website Daily Kos and the Service Employees International Union.
The survey comes just a few days after Democrats reserved $1 million in TV ad time on behalf of Bonamici ahead of the Jan. 31 special election. The high-dollar reservation raised eyebrows, even though party strategists said the spending was nothing more than an insurance policy for holding the seat.
The Democratic firm Public Policy Polling conducted the survey, which took the opinion of 979 likely voters in the district Dec. 13-14. The poll had a margin of error of 3.1 points.
Bonamici and Cornilles are running to succeed former Rep. David Wu (D), who resigned earlier this year.
The 1st district should be solid Democratic territory. President Barack Obama carried it with 61 percent of the vote in 2008.