I've no idea when the election numbers will be released but Cantor was expected to win by something like 35 points but he instead lost by 11 points.
Let's generously suppose that 20 points worth of voters figured the election was a guaranteed win for Cantor & they stayed home rather than going out to the voting polls. Maybe 10 - 12 points worth of voters were fed up with Cantor & decided to give the new guy a shot at representing the district.
Since there's been no recent mass immigration into Virginia, where did the number of votes come from to defeat Cantor by over 10 points? I think the democrats voted to affect defeating the #2 republican in the House!