Polls open tomorrow for the UK general election but Facebook already has a beat on the winner after polling an impressive 463,000 eligible British voters on the popular social network this past weekend.

And the winner is…Nick Clegg of the Liberal Democrats, Facebook announced on its blog about an hour ago. The Lib Dem leader scored an astounding 42 percent of the Facebook vote, at least 15 points above his most recent polling numbers. Rounding out the field: “David Cameron of the Conservative Party came second with 31 percent, while Gordon Brown of the Labour Party finished in third with 27 percent,” Facebook reports.

The poll took place over the past weekend. UK Facebook users were greeted with a pop-up to participate in the vote. Facebook is calling the interactive poll a first of its kind, adding “At the time of the last British election in 2005, Facebook wasn’t available to most people in the UK, while other social networking sites and services were in their infancy.”

This may look like PR puffery, but whenever you assemble such a large sample size it bears watching to see if the Facebook poll results are in line with the real thing. The other question we have is whether Facebook, as popular as it is in the UK, may actually sway last-minute undecided voters to the Lib Dem camp. If the “Likes” tally (770 in the span of just 90 minutes) is anything to go by, there could be an upset in the making.

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