The logistical questions would be huge. Let's say they start right after a big Trump win on Super Tuesday. They'd need to get some guy on the ballot in all 50 states in very, very short order, and it'd have to probably be someone not currently running to not get in the way of sore loser laws, and it'd have to be someone who has no future in elected office that they'd be throwing away by ruining their reputation this way.
Basically it'd have to be Mitt Romney.
What about Huntsman?
Getting three percent of the vote would not look very good.
Any establishment third party candidate would do much worse than a Trump third party candidacy.
