The history of 3rd party candidacies just isn't good. Our system, like it or not, is just not set up to accommodate it. In a winner take all system with no chance of coalitions, voters tend to "come home" to one or the other leg of the 2 party system. People vote against someone or the opposition party as much as they vote for a candidate or party (perhaps more). It is unlikely Perot's numbers would have remained that inflated.
Perot was erratic and a conspiracy theorist, as the election drew nearer people would consider those things more and more as the reality of actually electing the guy hit home. The sad thing is that he drew so many votes from the right and pretty much handed the White House to the Clinton's. Seriously, Perot was a nutter, no way around it when you look at the ridiculous conspiracies he was tossing around and yet there are probably quite a few people here who voted for him (my guess some of those same people would do it again with Trump).
I'm sorry to say this because I don't care for Romney, but he is right about the 47% thing. When you add up all their victim groups, minorities, etc, the Democrats really do start with about 47% or perhaps a bit more right now. If Trump ran indie he might, MIGHT, get a couple % of those (though I doubt it) leaving the Democrat at say 45%ish. Let's say Hillary is such a bad candidate that it even drops to 42% Dem turnout. The Republican is certainly not going to get less than 25% of the vote, especially considering how many Republicans in polls say they would never vote Trump. So let's say they run Jeb and get only 25%. That still means Trump only gets 33% of the vote even with that few % of nominal Democrats and some people who normally sit out. Those numbers would result in an electoral landslide for Democrats. That is the best case scenario too. The far more likely scenario is that the Republican scores much better and Trump winds up with 5-10% pulling mostly from the right of center. Again, a win for Democrats.
I just don't see it. Every election cycle this indie talk comes up and every election cycle said indie either implodes or it never materializes. The only way a Trump indie bid works is if someone on the left also runs indie and is equally as popular with the left sphere of voters. Like if Bernie Sanders decides to go 3rd party (he is actually a Socialist as it is). If you had 4 candidates, all reasonably equally popular, then yeah, you could have a real interesting election.
I don't think Trump will run as an independent unless the RNC and the other candidates and Rinos treat him so shabbily that he runs out of revenge. But idiots like McCain and Rove and a few others could accomplish it.
And nothing will convince me that Perot could not have won in 1992 had he followed through on the support he'd won and run a solid campaign until election day.