What if Chris Christie had run in 2012 and won?
Implausible? Not necessarily. In the buildup to 2012, there was a pretty strong draft Christie movement which included folks like Ken Langone and David Koch. They saw him as the only guy with the personality to take on Obama, and his fights with the public sector unions endeared him to the Kochs.
So what if Chris Christie and Paul Ryan (who is chosen for similar reasons as OTL) managed to beat Obama and Biden in 2012?
Republican voters would demand that Obamacare be on the chopping block, and it was far less popular in 2013 than in 2017, but the Democrats control the Senate here. Boehner would be more effective as speaker than Ryan was at rallying the votes.