The Democrats manage to scrape through the 2018 midterms fairly unscathed however in 2019 a deep recession sets in due to instability in the EU. President Hillary has ratcheted up bombing raids in Iraq and sent ground troops into Syria. With her presidency increasingly unpopular and a growing war weariness and unemployment at over 7% Rand Paul, the runner up in 2016 makes it through a crowded GOP primary field and runs an isolationist campaign which proves to be quite popular. He even gets to Hillary's left on civil liberties and manages to win by a fairly comfortable margin.
Paul/Snyder 303
Clinton/Castro 235
How the heck would Paul get 60% in Pennsylvania while losing Virginia? There aren't that many defense contractors!
That was an error, I meant to have it at 50%, though I suppose it's theoretically possible if he campaigned heavily in Philadelphia and Pittsburgh to cut into Hillary's lead while winning in a blowout everywhere else.