McCain vs. Obama: The online race

The poll numbers may be inconclusive, but John McCain's choice of Sarah Palin as running mate gave him one measurable boost: in web traffic. According to Nielsen Online, traffic to McCain's campaign website increased 242 percent during the week he named Palin to the GOP ticket. On the week ending August 31, McCain's site drew nearly 1.8 million unique visitors, compared to 524,000 the week before.

Obama's web traffic still vastly outpaced McCain's that week, boosted by the Democratic National Convention. For the week ending August 31, Obama's site drew about 3.4 million viewers, compared to 2.6 million the week before.

Another tidbit from Nielsen Online's latest report: Unsurprisingly, Palin drew substantial online buzz, measured in comments posted on message boards during the two convention periods. Off all convention speakers from both parties, Palin was the third-most-buzzed-about, after Obama (first) and McCain (second). She was followed distantly by Hillary Clinton (fourth) and Joe Biden (fifth).

Nielsen also reports that the McCain campaign substantially increased its online advertising in August, particularly in image-based impressions: 58.3 million in August, compared to 16.4 million in July, a difference of 254 percent.

Obama is still running far more image-based ads, though his advertising levels dropped dramatically in August: He placed 216 million image-based impressions that month, compared to 417 million in July.

McCain still leads Obama in sponsored-search link ads. He registered about 22 million sponsored search impressions in August, compared to 949,000 for Obama.