I, too wonder about who exactly picked McPain to be the nominee.
Part of the problem was the obvious weakness of the rest of the field. That was clearly on display during the convention when both Huck and Romney gave their speeches back to back. The former just trotted out the same tired jokes that he used in the primary - get some new material, seriously - while the latter used his time to blast 'Eastern Elites' - which makes zero sense whatsoever coming from him. While either one may have had their good points, neither had much potential as a candidate.
Republican voters did.