A part of being a "leader" is separating your actions from your own thought of how things might turn out.
McConnell, as the Republican leader in the Senate, should have acted with a confidence that Trump would win, despite his feeling that Trump would not win. Optimism is contagious, but so is defeatism. McConnell is a defeatist by nature, and therefore looks for reasons to not even try. He would rather make a deal that, in his mind, minimizes the loss.
Imagine what might-have-been had McConnell chosen to stand up for Christine O'Donnell in 2010 or Todd Akin and Richard Mourdock in 2012 instead of turning his back and running for the door.
-PJ
McConnell is the leader of Senators not the public. He did not go around attacking Trump in any case.
As for the races you reference, what makes you believe he has any real following outside his constituents?
He, like 99% of the GOP, did not know how to fight the Enemedia. In that respect he accurately reflected the party.
Only by destroying Fake News impact could those people have won and we had no one capable of that.
Those three you mentioned were not Senate material and lost. All three made major mistakes during their campaigns and that is why they lost. Those three are responsible for their loss and no one else.