http://thehill.com/blogs/blog-briefing-room/news/155415-trump-probably-run-as-independent-if-i-cant-win-gop-nodFor all those who want to say that any republican could've won this year, I give you this. This was a very bull moose/perot-like year, not necessarily a republican one, Bush would've won in '92 if it wasn't for Perot's character assassination attacks giving way to Clinton. Trump likewise specifically targeted the characters of all his main opponents, see how they went down after Trump's attacks. Cruz in particular, is a perfect example, was +1 v. Hillary in Mar 1, and collapsed to -10 on May 1.
Trump's plan was that if he lost the primary, he'd call the process rigged and 'unfair', tear down his main rival(s) and run independent.
http://www.nydailynews.com/news/politics/trump-refuses-rule-third-party-run-article-1.2587077He was already signalling 'unfair treatment' when the delegate selection process was underway:
http://thehill.com/blogs/ballot-box/presidential-races/276054-trump-slams-rnc-chairman-calls-2016-process-a-disgraceThis is what he was going to do.
This was not a republican year, this was a 1912/1992 type year.
Perot spent 66 mil in his 92 run, inflation adjusted that comes to ~ 100mil, which Trump was planning to spend (Trump ended up spending 66 mil anyway). He has the same net worth as Perot. Perot's main advantage was free media.
http://www.thedailybeast.com/articles/2015/07/24/how-donald-trump-could-fall-into-the-ross-perot-trap.htmlMost Trump supporters were saying from early on that they would go with him to a third party.
Now some will say, he would be afraid of losing? No, Trump didn't think he'd win the primary in the first place, he thought Jeb would win (like everyone else who ran did seeing as how none of them other than cruz who was specifically planning for a contested convention in case Jeb got less than 1237 had any serious campaign infrastructure) and just wanted to place second to him as a protest candidate.
http://www.xojane.com/issues/stephanie-cegielski-donald-trump-campaign-defectorIt would be an ego-trip for him to see how many votes he could win as an independent candidate alone, getting a high amount would be enough to boost his ego. For those states with loser-laws, he could just put his son's name, Trump Jr. on the ballot.
2016 was basically what would've happened had Teddy or Perot won the republican nominations in the years they ran in.