Can they get 217 other Republicans to vote for them?
Can someone always come up with conventional wisdom that proves Trump can't win? Sure, everyone in the media, all the political pundits, all the "Conservative" power players, and an awful lot of people here and elsewhere have been doing it since the day he announced that he'd run and are still doing it.
At lot is possible. How much if it is probable is hard to say, but I suspect the usual rules on how to determine probability no longer apply. Therefore, I say never underestimate the size of the rabbit Trump can pull out of a hat full of rioting mice.