He and his strategists calculated he stood a better chance of building a big support base and solidify it by running a populist anti-establishment campaign from within, through the Republican primaries, than attempting to run next year as an independent. So far, it's worked just great. The guy is a complete narcissist. He doesn't give a crap about the "Republican brand", he's just highjacked it for his own purposes. If he isn't chosen at the convention, if the establishment manages to block him, he will take his word back and his supporters and run as independent.

What the Republican establishment and the candidates are attempting against Trump now, they should have started long ago, when it might have gotten results and killed it in the bud.. and it puzzles quite a few analysts that they did not act sooner. Now they're more likely to strengthen the resolve of his supporters. I don't follow the news closely enough to really have an opinion about what's coming internally for the GOP, but I see some "experts" (Republican political scholars talking to the Canadian media) the whole Trump debacle may turn into the opportunity the GOP's establishment to pierce the abscess and rebuild the party on its more traditional ideological base. Some seem highly pessimistic about the establishment's reactions.

In any case, it's worrying but fascinating to follow the primaries from Canada this year. Never in memory I've seen so extensively covered and analyzed (in our great newspapers sure, but tabloids running their first page with the Super Tuesday, I've never seen that).