McCain. A worse campaign could've resulted in Obama winning a landslide given the circumstances. Heck, I dare say a better running mate than Palin and a weaker campaign from Obama could've tipped the election to McCain despite just about EVERYTHING going against him. Hillary on the other hand had no business losing to Trump, even with the Comey letter, it should've never been that close to where that decided the election.
Hillary Clinton was a severely compromised candidate even before she declared for 2016. But there was ample opportunity to mitigate the issues surrounding her email and Benghazi, and they failed. Completely. There is no excuse for 66% of people in Wisconsin thinking she is untrustworthy. You can't win as a Democrat in any year, against any opponent, with numbers like that.