“The accepted view is that if the RAF failed and the Blitz gone on, then Churchill would have been out,” Right, that is the point. I do not ACCEPT views. I challenge views.
“Halifax was favored by the majority in Britain as late as May of 1940” How do we know that? Polls? Elections? We had plenty of examples where some people were seen as favourites before an election then they lost the elections. The British are not good in accepting defeat as shown by their history.