Okay, actually 50.96%, according to Dave Wasserman's page. But that rounds up to 51%. And it was nice to see it hit that number on the Wikipedia page for the 2012 Presidential election.
I'm still hoping that he reaches 51.03%, to put him ahead of McKinley in 1896 and, with Jackson, Grant, FDR and Ike, one of only five to have achieved that high a percentage twice.