What is the logic behind
Protests by candidates the trump is unfit for the presidency. That he is a liar and a con man but should he win the race to the nomination, Cruz, Rubo, and Kasich all swear that they will vote for the party nominee.
Is that party loyalty lunacy to vote for a candidate that is a con man and a liar? What changed between their remarks and their ballot? His winning clears him from previous sins??? Alas I would vote for anyone I thought unfit for office and all three of those dudes made that claim.
Where is Jeb when you really need him. I'll bet he won't vote for trump. Nor will lindsay graham.
Re: What is the logic behind
I doubt that any of them would lift a finger for Trump although they might hold their peace.
The absolute nightmare scario for the GOP is if they dump on Trump too soon (although currently don't have another plan) and he has enough time to get a serious third party campaign going.
On the other side, Bernie has said, literally from day 1, that he would not run as a third party candidate and would support the nominee. He and Ms. Clinton have had a spirited but thus far civil debate.
Of course he doesn't have to prove his is bigger than hers either.