Noam Scheiber suspects that Ryan hurt the ticket:
[J]ust in case anyone was tempted to forget some recent history and insist that unleashing Ryan would have pushed Romney over the top, there was one place Romney simply couldn’t keep him hidden: Southeastern Wisconsin. In 2008, before Ryan became the leader of the GOP’s war on government, and long before Romney thrust him and his bold ideas into the national spotlight, Ryan carried his Wisconsin congressional district by a 29-point margin. On Tuesday, he won it by a mere 13-points, even as Obama’s Wisconsin margins fell in half. If Republicans want to try replicating this special form of magic on a national scale, I’m sure President Biden will be the first to thank them.