In the report, "Searching for the Next President," Chicago-based Web marketing analytics firm AdGooroo found that Obama sites are drawing more than 20 million visitors per month, compared to about 4 million for McCain.

Obama's huge traffic advantage is not a big surprise, given that the Democratic presidential candidate has relied heavily on the Internet to build enthusiasm for his campaign and to raise money.

Despite his smaller Web presence, however, McCain is drawing nearly 11% more traffic from politically neutral sites than the Obama campaign. If the race comes down to undecided voters, as some political experts have suggested, then that finding could be a positive signal for the Republican candidate.

At the same time, McCain also has a higher proportion of sites directed against him, at 29% to 15%.

In comparing the search marketing strategies of the campaigns, AdGooroo found that while Obama has the advantage in natural search rankings, McCain has been more active in paid search advertising.

Obama ranks on the first page of unpaid results for 117 keywords, compared to only 67 for his rival. Among the organic search terms that Obama ranked high on were "affordable health plan," "Barack Obama birth certificate," and "message alert." The last term was derived from Obama's novel announcement of running mate Joe Biden via text-message.

In paid search, by contrast, AdGooroo found 226 keywords being targeted by McCain, compared to 174 by Obama. The McCain campaign has gained attention for its paid search prowess, most notably by outbidding Obama on terms such as "Joe Biden."

And when "Sarah Palin" emerged as one of the most-searched terms on the Web, McCain had ads ready inviting users to learn more about his own running mate, a recent study by SEM firm Didit.

Like that research, AdGooroo found McCain had more search terms tied to specific issues than Obama, including "abortion," medical saving plan," and "affordable housing." Obama's keywords mainly targeted variations of candidate names on both sides.

If McCain has used a wider variety of paid search terms, Obama has been quick to add topical keywords such as "lipstick" and "Paulson," allowing them to take advantage of temporary surges in traffic, according to the report.

AdGooroo also identified 17 negative paid search ads by Obama, but only three from McCain. Given the wave of TV attack ads the McCain campaign ran against Obama, the much higher proportion of negative ads from Obama seems surprising.

Among them were ads with tag lines such as "Elect Obama, Not McSame," "Is McCain a Maverick?" and "Is McCain Out of Touch?" Some of them point to new TV ads.

For the study, AdGooroo quantified the Web site activity, Internet reach and search engine marketing keyword selection of both camps, based on data collected from Sept. 1-22.

Sites were categorized by their stance toward the candidates: for, against, or neutral. AdGooroo said a few instances required a judgment call. A blog that focused on Obama but featured both positive and negative articles would be classified as neutral.

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