The National Republican Senatorial Committee has been quietly outspending its opponents on sponsored Google search links that steer Web users looking for information about Democratic candidates to NRSC-run attack sites.

The NRSC is buying the links for seven tight Senate races: Alaska, Colorado, Louisiana, Minnesota, New Hampshire, New Mexico and Oregon. A Google search for Anchorage Mayor Mark Begich, for example, yields a prominently placed link to MarkBegichFacts.info. The NRSC-operated site alleges, among other things, that the Democrat has a history of paying his property taxes late and that he once evicted a tenant on Christmas Eve.

"I think it's definitely been worth it," said Rebecca Fisher, communications director for the NRSC. "In this world of online news, it's a way to cut through the massive amount of information out there."

New data suggests these paid links may help sway undecided voters. A recent survey by Didit, an Internet-search marketing firm, found that respondents who followed sponsored links to political sites were 31 percent to 40 percent more likely to change their opinion of a candidate.

"From a pure branding point of view, whether the link is positive about you or negative about your opponent, it has a huge amount of power and a huge amount of influence," said Daljit Bhurji, managing director of London-based Diffusion, a social media communications agency.

But despite the prominent placement of the NRSC's search links, many Democrats haven't quite caught on to the Republican strategy. Several campaign representatives were familiar with the NRSC's attack sites, but most had not realized their candidates were also the targets of a Google advertising blitz.

"I don't know that we were aware that they were purchasing this," said Julie Hasquet, Begich's press secretary.

Tara Trujillo, a spokeswoman for Rep. Mark Udall, D-Colo., was acquainted with BoulderLiberalMarkUdall.com, a site whose banner juxtaposes Udall's face with a burning American flag. But Trujillo said she hadn't noticed the NRSC's paid links that appear next to Udall's "organic" Google search results.

Republicans, meanwhile, boast that their emphasis on aggressive and often negative search engine advertising is no fluke.

"We've been evangelizing," said Rebecca Donatelli, president of campaign strategy firm Campaign Solutions and managing partner of Internet advertising agency Connell Donatelli Inc., both based in Alexandria, Va. Donatelli is helping John McCain buy sponsored links in the presidential race. "It's so effective and the measurements are so strong."

McCain purchased 21.6 million sponsored link impressions in August, up from 15.1 million in July, according to Nielsen Online. Meanwhile, the same report shows that Democratic nominee Barack Obama bought just 949,000 impressions in August, down from 1.2 million in July.

The Obama camp disputes the Nielsen figures, and a spokesman maintained that "search advertising accounts for a large portion of our new media strategy." The campaign recently sponsored links for the search terms "Palin" and "Sarah Palin," directing Web users to a TV ad on the Obama campaign site called "No Maverick."

And not all Democratic Senate hopefuls are out of the loop, either. Matt Canter, a spokesman for Jeff Merkley's campaign in Oregon, said he is aware of the NRSC's strategy. The Merkley camp has bought sponsored links in the past as well, he said, but for search terms like "pro-choice" and "renewable energy," in an effort to draw issue-interested voters to the official Merkley Web site.

Hannah August, a spokeswoman for the Democratic Senatorial Campaign Committee, said the group sometimes purchases Google links. But those, too, are usually intended to lead Web users back to a candidate's official page, she said.

Bhurji, the public relations director, said these links can be effective "because when people look at a page, they look at how much space your brand takes up and make judgments." However, he added, that does not excuse Democratic ignorance of the NRSC's tactics.

"The Democrats shouldn't be so naive as to think that the Republicans won't be bidding against them for these terms," Bhurji said.

Despite the Republicans' apparent Google savvy, Bhurji said both parties have yet to tap search engine advertising to its full potential.

"If you put 'lipstick on a pig' into Google, there are no links to any Republican or Democratic sites," he said. "But I think there's a very steep learning curve for this stuff. We may see them get better in the next 50 days."

CORRECTION: The original version of this report misstated Mark Begich's status as mayor of Anchorage.