I don't know how deep division in the Repub party goes, but it is apparent they cannot govern. The GOP is very worried about Repub senators surviving a Trump nomination...How worried? Well, a private memo went out on how to deal with Trump being the Repub nominee...
PRIVATE MEMO LAYS OUT HOW THE GOP WOULD DEAL WITH TRUMP AS ITS NOMINEE
In a seven-page confidential memo (dated Sept 22) that imagines Trump as the party's nominee, the head of the National Republican Senatorial Committee urges candidates to adopt many of Trump's tactics, issues and approaches - right down to adjusting how they dress and how they use Twitter.
Above all, they should appeal to voters as genuine and beyond the influence of special interest.
-Wash Post, December 2, 2015
Sen McCain, speaking at a Christian Scientist Monitor breakfast this week about a Trump nomination, recalled when Barry Goldwater got the GOP nomination and the damage it did to down-ticket candidates, "I think obviously we all know in history when you have a weak top of the ticket, that has significant impact".