A victory is not impossible—just improbable. We need a large turnout for Ken and a somewhat depressed Dem turnout. The Dems have already built up a lead based on polls of early voting. The Dems are very good at rounding up their voters and getting them to vote prior to election day. No doubt some fraud is also involved.
Ken also needs to tie McAuliffe to Obamacare. I think he did that in the debate or at least said he would keep Obamacare out of VA.