We all know by now that if you could vote on the Internet, Barack Obama would already be president. His Website has always attracted more traffic than those of other candidates. Unaffiliated video-endorsement site YouBama popped up spontaneously to collect video endorsements from supporters. MoveOn.org is getting its constituents across the Web to rally behind him. Even Silicon Valley digerati like Marc Andreessen love him.

Today, Compete shares some more numbers (in table above) that show Obama beating Hillary Clinton 2 to 1 in Web traffic, 4 to 1 in Wikipedia article readers, and 10 to 1 in time viewers spend watching their videos on YouTube. Compete also measures something it calls “FaceTime,” which is the amount of time spent with each candidate across several leading social networks and media sites (Facebook, MySpace, Flickr, MeetUp, YouTube). Obama trounces Clinton there as well, with 78 percent share versus 21 percent. And among Web surfers in Pennsylvania, which is holding a big primary on Tuesday, April 22, twice as many people are visiting Obama’s official Website than Clinton’s.

This doesn’t necessarily mean Obama is going to win Pennsylvania. The Web population still skews younger than the general electorate, but his strength on the Web is definitely one of Obama’s competitive advantages.