The Democratic Congressional Campaign Committee has increased its TV airtime reservation in the Oregon special election by nearly $300,000, indicating the party could be concerned about the race in the solidly Democratic district.

The DCCC has now reserved $439,000 worth of network airtime for the next two weeks in the Portland-based 1st district, according to a Republican source with knowledge of the buy.

The increase indicates the committee is taking Republican Rob Cornilles’ candidacy seriously and is uncomfortable with the possibility of losing the seat of former Rep. David Wu, who resigned in August amid a scandal. Cornilles is facing Democratic state Sen. Suzanne Bonamici, who turned in strong fundraising reports through the Nov. 8 primary.

“In this environment, with an untrustworthy potential self-funder like Rob Cornilles and with voting in January when voters are not accustomed to voting, we’re not taking anything for granted,” a DCCC spokeswoman said in an email.

Roll Call reported earlier today that the DCCC had purchased $124,280 for network TV ads and $24,170 on cable.

The DCCC is airing an ad against Cornilles that ties him to the tea party and says he has plans that would threaten Medicare and Social Security. Bonamici and Cornilles each launched ads of their own in the past couple of days, both of which are positive spots.

The district, which stretches from downtown Portland to the Oregon coast, voted 61 percent for Barack Obama in the 2008 presidential elections. National Republicans have so far given no indication that they intend to spend heavily to win the district.

The National Republican Congressional Committee spent heavily to defend a GOP-held district earlier this year, when Rep. Mark Amodei easily won the special election in Nevada’s 2nd district.