The clamor you are hearing for Paul Ryan for VP is not about helping the Romney candidacy. It's about controlling the Romney campaign—and ultimately the Romney presidency. It's about forcing a platform on Romney, and then dictating the agenda for that presidency's first year. The platform happens to be suicidal, and the agenda impossible, but that does not matter to the Ryan advocates. They take the old Tammany Hall point of view: "Better to lose an agenda than lose control of the party."
In that sense, the Ryan proposal is a test of Romney's leadership. If he accedes, it's a big surrender of control—and a surrender to many of those who most opposed (and who inwardly continue to dislike) his nomination.