All good points but don't look to the other candidates to honor their pledge to support Trump OR Cruz. They're liberals and liberals don't keep their word. That's why I say it was a trick.It exposes the true agenda of the establishment GOP. We've suspected for a long time they were in the tank for the Democrats and this election is showing that to be the case. Trump was tricked into signing the pledge and therefore he is not morally obligated to honor it. His supporters will vote for him whether he runs as a Republican OR Independent.
I don't think Trump was tricked into doing anything. He is not going to run 3rd party and never was. The threat that he may, only comes into play if he is not the GOP nominee. If he is not the nominee it looks like it will be either Cruz or Carson. He wouldn't run 3rd party against either of them, there is not enough difference in their views. If the party were poised to nominate Jeb, it might be a different story. I think Trump saw the establishment candidates have no chance and so, why not sign the stupid pledge that seemed to be the only thing anyone wanted to talk about? I think it was a good move on his part, it showed that he is willing to bend and doesn't mind playing nice. It also means that he can hold every one of those other candidates to the deal-- they MUST support him now, if he wins the nomination.