Outside groups made the difference for some Republicans

In a number of key races around the country, aggressive and meticulously targeted spending by independent conservative groups appears to have helped produce dramatic results for Republicans.

Unlike Democrats, who relied heavily on financial assistance from unions and Democratic Party committees, Republican candidates got their boost from advertising, mailers and get-out-the-vote drives financed by more than a dozen newly formed conservative groups.

Those groups employed a two-pronged strategy: First, they poured much-needed cash into districts where Republican candidates lagged behind in fundraising. Second, they sent millions into what were once considered safe Democratic districts in an attempt to thin out Democrats’ resources.

The strategy appears to have been a success. In an election cycle where Democratic candidates and party committees had out-raised Republicans by about $168 million, outside conservative groups, armed with $187 million, were able to strategically and successfully leverage that money to produce results for the GOP.

In the 74 House and Senate seats that had switched party hands by early Wednesday morning, 57 were won by Republicans who held the advantage in spending by outside groups, according to an analysis by the consumer advocacy group Public Citizen.

Republican Mark Kirk enjoyed the greatest advantage in non-party outside spending in his winning bid to represent Illinois in the Senate. Thanks to large and consistent ad buys by groups such as American Crossroads and Crossroads GPS — big spenders that were formed this year by Karl Rove and other GOP strategists — Kirk held an $8-million advantage in outside money over his Democratic opponent, Alexi Giannoulias.

In the House, Republican Mick Mulvaney topped the list of outsider support with his successful bid to replace 14-term incumbent and chair of the powerful House Budget Committee, John M. Spratt Jr.

In the final two weeks of the campaign, non-party groups opposing Spratt spent nearly $500,000 in his South Carolina district, compared with just $6,000 spent by groups in support, according to data compiled by the Sunlight Foundation

In southern Virginia, 14-term incumbent Rick Boucher was defeated after conservative groups waged a costly ad campaign that went unmatched by groups on the left.

On the Iron Range of Minnesota, 17-term incumbent James L. Oberstar, chair of the House Transportation Committee, was swept from office after a late October storm of conservative group advertising on Duluth television.

“We were able to go places where Democrats were comfortable and require them to start spending money,” said Carl Forti, political director at the Crossroads groups, citing Oberstar’s district and others. “For us, it was an effort to expand the field.”

Liberal groups did not spend a single dollar advertising in Oberstar’s district, according to the Public Citizen analysis. But the onslaught forced Oberstar to run the first negative ad of his career.

kim.geiger@latimes.com

Times staff writer Tom Hamburger contributed to this report.