I'd say the evidence that Jeb! Bush will never emerge from the single digits is already convincing but here's another log for the fire.
Donald Trump is unhinged. His "policy" proposals are not serious.
— Jeb Bush (@JebBush) December 7, 2015
Jeb! has made it fairly clear that he'll vote for Donald Trump no matter what because fascism is still better than Hillary Clinton apparently. A majority of Republican voters may agree but there's no conviction to be found here. You can't defeat Trump by surrendering to him.
Jeb is hardly alone. A number of Republicans have rushed to condemn Trump after he called for banning all Muslim immigration, but none of them are willing to say they will vote for someone else.
Speaker of the House Paul Ryan, for example, says Trump does not represent the party but he will still support him.
Ryan said at a press conference that Trump's comments are "not who we are as a party" and violate the Constitution. [...]
Asked if he'd back Trump if he was nominated by the party in 2016, Ryan responded, "I'm going to support whoever the Republican nominee is and I'm going to stand up for what I believe in as I do that."
With each admission that the party will get behind Trump regardless of what heinous shit comes out of his mouth we grow one step closer to his nomination.
I imagine the Republican autopsy of 2016 will conclude that they should have taken a tougher stance against Donald Trump even if he isn't the nominee. Trump has a virtual monopoly of the entire conversation on the right.