This seems to be the week for Trump tax mysteries. One mystery is why Donald Trump, unlike every other major party nominee in modern times, is refusing to release his tax returns. The other is why, having decided that he needs experts to clean up his ludicrous tax-cut proposals, he chose to call on the services of the gang that couldn’t think straight.

On the first mystery: Mr. Trump’s excuse, that he can’t release his returns while they’re being audited, is an obvious lie. On the contrary, the fact that he’s being audited (or at least that he says he’s being audited) should make it easier for him to go public — after all, he needn’t fear triggering an audit! Clearly, he must be hiding something. What?

It could be how little he pays in taxes, a revelation that hurt Mitt Romney in 2012. But I doubt it; given how Mr. Trump rolls, he’d probably boast that his ability to game the tax system shows how smart he is compared to all the losers out there.

So my guess, shared by a number of observers, is that the dirty secret hidden in those returns is that he isn’t as rich as he claims to be. In Trumpworld, the revelation that he’s only worth a couple of billion — maybe even less than a billion — would be utterly humiliating. So he’ll try to tough it out. Of course, if he does, we’ll never know.