If Perot had not mishandled the threats to kill him and his family, he would have been President.
At the present pace, I don't see anyone catching Trump--if there is somebody who might, it is Ted Cruz which would be a high class result. And Trump is not going to run a third party campaign against Cruz.
Behind the scenes, there are widespread discussions about peremptory action to install Bush the Third as the nominee. If that happens, all bets should and presumably would be off--in a race between Mrs. C and Bush 3, a third party candidate should be the winner.
My own personal assessment of the race really doesn't involve Mrs. C or this widespread horror at running against her: I don't think Mrs. C has a prayer of being the Dem nominee; if perchance I am wrong, I would view a contest with her as a real opportunity.
Presently, I think the high probability is that Biden will be the Dem and that he will be a much more difficult opponent than anyone on the Conservative side expects.
On our side, the core constituency is not going to turn out for Bush or Casich or any of the Romney style retreads; in a race between Bush installed by force by the party apparatus, against either Mrs. C or Joe, I would think a third party candidate would be a certainty and would have a good chance to win.