(Reuters) - An Oregon special election in which national Democrats have sought to paint the Republican congressional candidate as a Tea Party radical foreshadows a tactic the party will employ in its quest to take back Congress seats lost in the 2010 election.

The Democratic Congressional Campaign Committee has spent about $1.3 million in the race, half of it opposing Republican businessman Rob Cornilles in Tuesday's election to replace disgraced Democrat David Wu.

Television advertising and a Web site run by the committee, which supports Democrats in House races, slam Cornilles for referring to himself as the original Tea Party candidate during a previous congressional run.

The race between Cornilles and Democratic state Sen. Suzanne Bonamici is a preview of an already heated election year when outside groups are pumping money into opposition advertising, and Democrats plan to attack conservatives who have curried favor with the Tea Party.

There is no doubt that races across the country will be about a contrast between Tea Party extremism that protects the ultra-wealthy versus defenders of the middle class and Medicare, said Jesse Ferguson, a spokesman for DCCC.

But in each district, the message will fit the district, the local values of the community and the candidates running.

The race has attracted an unusual level of interest for a traditionally safe Democratic seat. Obama easily won the Portland-area district in 2008, and Wu beat Cornilles in a 2010 election year that heavily favored Republicans elsewhere in the country.

Wu, who was in his seventh term, in July announced he would resign after a sex scandal. The race to replace him will wrap up on Tuesday, when Oregon's vote-by-mail ballots are due.

The election has drawn almost $2 million in independent expenditures since November despite the fact that early polling showed Bonamici, a former Federal Trade Commission lawyer who has served in the Oregon Senate since 2008, with a considerable lead.

CYBER ATTACKS

Democrats have made Cornilles' Tea Party statement, made at a May 2010 event, a central part of their attack on the Republican, who runs a sports-consulting business.

Teapartycornilles.com, a site paid for by the DCCC, features the quote, raps Cornilles for his extreme opposition to abortion and claims he supports ending tax cuts for middle-class families.

A fake Twitter account, @TPartyCornilles, sends out comments such as, Will Republican Rob Cornilles try to run from his extreme Tea Party anti-choice record in tonight's debate?

Many Republican candidates attended Tea Party events and sought endorsements from local chapters in 2010 to fend off primary challenges or third-party candidates as support for the Tea Party's small-government mantra swelled.

But public sentiment has since shifted, with Tea Party-sanctioned Republican freshmen in the House of Representatives taking much of the blame for standoffs over the extending debt ceiling, extending payroll taxes and other issues in 2011.

Oregon Republicans say all the Democratic-aligned money is proof Democrats are worried about losing more seats in 2012. Cornilles' campaign recently released an internal poll showing him within four points of Bonamici.

I think the DCCC has kind of hit the panic button here...the more they've spent, the closer the numbers have gotten, said Greg Leo, chief of staff for the Oregon Republican Party.

I don't think it's really an accurate referendum on the Tea Party, nor is it an accurate description of Rob Cornilles, Leo said, pointing to the candidate's refusal to sign Grover Norquist's no-tax pledge as evidence Cornilles is not driven by the Tea Party.

The multi-media approach to attacking Tea Party-aligned candidates could be employed in other districts leading up to the November general election when all House seats and a third of the Senate are up for re-election.

If somebody comes out as a Tea Partier, we're going there, said Trent Lutz, executive director of the Oregon Democratic Party. If they drape themselves in the Tea Party banner, then absolutely it's something that we will discuss.

Democrats also have run sharp ads in Oregon claiming Cornilles has overstated the number of jobs created by his consulting business. A coalition of women's groups paid for ads and mailers criticizing the Republican for his pro-life views.

The National Republican Congressional Committee pitched in on a coordinated ad buy with the Cornilles campaign, but nearly all of the outside spending reported in the race came from Democratic groups.

Republican ads say Bonamici lacks experience creating private sector jobs and that she has voted to raise taxes while in the state Senate. One Cornilles ad tries to hurt her image by linking her to Wu.

(Reporting By Emily Stephenson, additional reporting by Alexander Cohen; Editing by Cynthia Osterman)

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