Twenty percent of the GOP won't vote for Rudy because he is so pro-choice. Another 25 percent have serious reservations.
And that doesn't even start to get at Rudy's problems he will have with the NRA bloc.
Faced with a hillary clinton alternative, most of those people have the wits and moral compass to hold their collective nose and pull the R lever. And then he has the pickup of independents and even some Ds.
In other words, the situation is not nearly so dire as you fantasize.