UPDATE:Add Ryan Ayotte and McCain to the list
The GOP Establishment's Maine's Senator Susan Collins and Illinois Senator Mark Kirk for example will have torn the Republican Party into three, unless Donald Trump wins the election. What makes Kirk's defection so ridiculous is he is going to be slaughtered in Illinois so he will be a loser and a turncoat and good riddance
If Trump loses, and of course Collin, Kirk et al actions would be a considerable factor in such a loss, it is impossible for the party to stay permanently unfractured after November. Paul Ryan being holier than thou over an eleven year old conversation and refusing to attend an event with Trump is disgusting
The fifty Republican security analysts who signed an open letter declaring Trump unfit for the presidency is a matter that Trump, rightly, shrugged off as coming from a 'failed Washington elite." Their contribution, if any, to a Trump defeat would be be negligible and Trump's dismissal would resonate with anyone who took any notice of the signatories.
The scattering of elected Republican officials, three Congressmen in particular, who have advised they won't vote for Trump are also, in the great scheme of things, unlikely to have any bearing on his Electoral College vote, but it might have an affect on their subsequent careers at primary time.
Senator Collins betrayal of the GOP, and betrayal it is, marks a bridge too far. Even Nixon campaigned for Goldwater whose campaign makes Trump look Reaganesque, that Collins could not also be loyal, if not to Trump then to the millions who chose him in the primaries, marks an irreparable breach.
Further Maine, where recent polling had Trump leading in one Electoral College vote district and whose four votes could be crucial makes Collins betrayal even worse than it appears.
Collins is a respected, long serving senator in a time of genuine and widespread disaffection for politicians, and given Trump's apparent problem with women voters her attack compounds the situation.
If via the desertion of Collins, the breaching of the "contract' to support the nominee by Jeb Bush and others, Trump loses then there is no possible way for the party as currently constructed to stay united.
There is no possible way that Trump supporters can work with the "#NeverTrump" irreconcilables who are deluding themselves if they think the party will unite after November. Why on earth should any Trump supporter support any candidate that these betrayers support in future
There will be three distinct groupings. The D.C. establishment as represented by the Bush/Romney/Graham/Ryan element, the grass roots Trump supporters and the Cruz "constitutional conservatives."
There is no possible way for these three utterly opposed groupings to stay together, the days of
cynical "unity" would be over and for any member of these three groups to support the other would be an abhorrent show of utter cynicism.
If Trump loses the populist "Trumpist" element would respond to the leadership vacuum (presuming Trump steps down) and a Sarah Palin type, perhaps Rubio (if not Palin herself) who combines the qualities of religious values, populist roots and mutual respect with a center-right policy.
Then again populists deserted Rubio over his immigration policy and his attacks on Trump, so it is hard to see them trusting him ever again. It is of course not unimaginable that Rubio would desert to the establishment if Trump loses and make a bid for the nomination that way-good luck to him and his "only a Hispanic can win Florida" sure to come meme.
This group, which has to be a new party for obvious reasons of utter incompatibility with the backstabbers in D.C. would have the widest popular voting support.
It is conceivable that if personal animosities could be overcome and conservative leaders do not attack Trump overtly then some sort of coalition with the populists could be created, but if not there is the makings of a regional party (it would of course have no effect in the east where Cruz was battered in the primaries).
As for the establishment they would be welcome the the name of "Republicans as they disappear down the rabbit hole where the Federalists and Whigs preceded them. Their candle will be a brief, unloved and unlovely flicker as its light, such as it is, splutters out. It is unimaginable that the vast populist movement that came to support Trump in their millions could be led by Lindsay Graham, Jeb Bush and cohort.
The transition to a new populist party will be quick and not painful, rather like a butterfly emerging from a dusty cocoon casting off the detritus of change. It may come to pass that populists will thank the likes of Collins,Ryan and Graham for making this emergence possible. It would be better of course for their likes to be swept away by a Trump landslide but if that does not eventuate four years of renewal and their being discarded will be effective.