Republican presidential candidate Donald Trump holds a signed Republican loyalty pledge. (Richard Drew/AP)

When Donald Trump held a news conference at Trump Tower in the fall to announce that he had signed a pledge to support the Republican presidential nominee and not run a third-party candidacy if that nominee wasn't him, many people treated it as a big deal.

After all, he signed a (non-legally-binding-in-any-way) piece of paper! And said he would stick to it!

These people, obviously, have never met Donald Trump. Trump, throughout this presidential campaign and in his broader adult life, tends to be guided by a single principle: What's the best thing for me? Right now?

So no one should have been surprised in the least when Trump told CNN's Anderson Cooper at a town hall event in Milwaukee on Tuesday night that his loyalty pledge was no longer binding. Here's the exchange:

ANDERSON COOPER: Before we go back to the audience, I want to ask you a question I asked to Senator Cruz as well. More than six months ago you pledged to support the Republican nominee, whoever that may be.

A lot has changed since then. It sounded, when I was pressing Senator Cruz on it, sounded like he was saying he'd have a hard time supporting somebody who went after his wife.

TRUMP: Honestly, he doesn't have to support me. I'm not asking for his support. I want the people's support.

(APPLAUSE)

COOPER: Do you continue to pledge whoever the Republican nominee is?

TRUMP: No. I don't anymore.

COOPER: You don't?

TRUMP: No, we'll see who it is.

Later, as Cooper probed on Trump's backing away from his initial pledge, the real estate mogul explained that "I have been treated very unfairly" by the Republican National Committee. His evidence for that "unfair" treatment is the following: 2012 GOP nominee Mitt Romney gave a speech arguing against Trump as the GOP nominee; Ted Cruz has been mean to Ben Carson (a Trump endorser); he won Louisiana but got out-organized by the Cruz forces in the battle for actual delegates to the Republican National Convention.

Even if you buy all of those claims as actual evidence of unfair treatment, a total of zero of them have anything to do with the RNC or its official functions in a GOP presidential primary.

I think Trump knows that. When he initially said that he would adhere to his loyalty pledge assuming he was treated "fairly" by the Republican establishment, he was building in an easy out for himself. Fairness is in the eye of the beholder after all -- and I know Trump knows that. Is it unfair that some people within the party don't think Trump is either conservative or electable? Not really. It's just politics. But by taking an alleged stand on "fairness," Trump is able to lay claim to the moral high ground. If only the Republican Party had treated me fairly, I might have been able to support their nominee. Or I wouldn't have had to run a third-party candidacy. You get the idea.

Trump never had any intention of staying true to that piece of paper he signed at the behest of RNC Chairman Reince Priebus. At the time, the field was still large, no one had voted yet, and there were questions swirling about whether he was a "real" Republican. Trump signed the pledge -- and made a giant event out of it -- because it helped solve a problem for him. Period. Now, with the delegate lead and his front-runner status totally cemented, Trump feels no compunction in walking away from the pledge. None. (Worth noting: Neither Cruz nor John Kasich was willing to unequivocally state his support for the eventual GOP nominee, either.)

Trump does what is good for Trump. Always. When it made sense to be for Republican unity, Trump was for it. Now that he doesn't need to be for it anymore, he isn't. His logic is totally transparent.

So, if you are stunned at Trump going back on his loyalty pledge, you just haven't been paying attention.