Artist Shepard Fairey's spin
on Barack Obama

In the month of May, Barack Obama's campaign website generated 1.7 million more hits than John McCain's, reports Nielsen Online (via Advertising Age).

May was the last month of Democratic primary season.

More data:

• In total, Obama drew 2.3 million unique visitors in May; McCain reaped just 563,000.
• The Obama campaign ran 105 million ad impressions in may, versus McCain's 8.6. However, McCain ran three times more search impressions than Obama did. Neither candidate has committed a significant amount of money to online advertising, says AdWeek.
• In June, Obama drew twice as much buzz on blogs: he was referenced in 0.75 percent of all consumer discussions. McCain was referenced in 0.39 percent.

Obama's success was attributed in part to his campaign's social networking savvy, as well as third-party efforts — including some by celebrities — to create Obama ads and web mash-ups. (It was recently revealed that Chris Hughes, a Facebook founder, left Facebook last year to help design My.BarackObama.com, Obama's social network.)

McCain is nonetheless expected to gain online traction as Election Day draws near.