Edward J. McCaffery is Robert C. Packard trustee chair in law and a professor of law, economics and political science at the University of Southern California. He is the author of " Fair Not Flat: How to Make the Tax System Better and Simpler ." The opinions expressed in this commentary are solely those of the author.

(CNN) Donald Trump doesn't want the world to see his secrets -- but seemingly only when the spotlight would cost him money. When forced to disclose costly information to public scrutiny, "Don't-Disclose Donald" lashes out. It seems self-evident to Trump that his making or keeping his own money is a reason for doing or saying just about anything. That's not usually the order of priorities for politicians.

Take his shocking attacks on the federal judge in the Trump University case, Gonzalo Curiel. After Curiel ordered Trump to fork over hundreds of page his Trump University playbooks, Trump went on a 12-minute, racially-infused tirade in which he told an audience that had no reason at all to care that he "could have settled" the cases, but he didn't want to -- because then he would get a reputation as a "settler" and "others would sue."

Judge Curiel's decision to make Trump disclose damning evidence that will almost certainly complicate if not drive up the price of any settlement apparently justifies racist attacks — a position Trump has continued to defend

There's the same pattern with Trump's $1 million contribution to a veterans group. After stonewalling those calling for him to disclose just how much money he had raised and personally given for as long as possible, Trump gave a combative press conference after Memorial Day, claiming he wanted to keep his giving "private." The facts strongly suggest that the journalists had guilted Trump into actually writing a check.

The Donald generally loves the media when it is paying attention to him. But when journalists force a disclosure that costs him money, they become "dishonest" and "sleaze."

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Which brings us to Don't-Disclose Donald's puzzling refusal to release his tax returns, as all major-party candidates for president for the last 40 years have done. Trump says he doesn't want to disclose because he's being audited. But like so many things Trump says -- take his accusations of bias against Judge Curiel or of dishonesty among the press corps -- the "audit defense" does not hold water. This is not just because there is no legal impediment to Trump's releasing his tax returns while under audit, as the IRS has said and as Richard Nixon, of all people, did

The fact is that when Hillary Clinton, Bernie Sanders and scores of other candidates release recent returns to the public, they risk scrutiny that could trigger an audit -- this can happen up to three years after a return is filed. A disclosure that prompts an audit is arguably worse than disclosing in the midst of an audit (which Trump claims is "continuous" and "routine" in any event.) That's just part of the cost of running for president -- a price the Donald does not want to pay.

What can Trump's "audit defense" really mean? There has been much speculation about why Trump is not disclosing his returns -- he makes less than he claims, gives little or nothing to charity, pays low or no taxes. But being audited is irrelevant to these reasons: disclosure would show such matters whether any candidate is being audited or not, and Trump does keep saying he will disclose after the audit.

So what is the reason behind Trump's reason for not disclosing? Trump acts as if it is obvious and easily understood that no one would release returns while being audited -- as it would be were Trump "simply" a rich person concerned with his money, alone. Just like all good criminal defense attorneys tell their clients to say as little as possible to investigatory authorities, lest the State become aware of other possible crimes or evidence, Trump's tax team may well be advising him not to disclose his returns lest the private sector help the government find questionable aspects of the return.

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Tax professionals call the strategy of trying to hide aggressive positions from the IRS the "audit lottery." An aggressive taxpayer being audited plays the audit lottery by hoping that an underfunded and overworked IRS (and note that Republicans like Trump want to keep the IRS underfunded will simply "miss" questionable aspects of a tax return. Trump wants to win this lottery.

The risk in releasing his tax returns that Trump himself points to as obvious is simply and purely that disclosure might end up costing him money. Hillary is willing to run the risk, but not Don't-Disclose Donald. Trump is not terribly worried about disclosures of his sexual peccadillos or prowess ; or of inconsistent policy statements or outright lies ; or of offensive statements about all sorts of people and things. Such disclosures, which to others would pose risks of sanction, shame, or losing elections, are the stuff of daily life and hourly tweets for Trump. But being forced to disclose something where the disclosure might cost cash is something else. Trump is cheap.

In all three cases, Trump is not just bashing the public's right to know, an independent judiciary, and other hallowed aspects of democracy. He is clearly and consistently resisting anyone else's authority to make him disclose information. He is also putting the value of his money ahead of all else: the Trump University plaintiffs, veterans, and the American taxpaying public, respectively.

Trump's campaign for president rests on the notion that he is a successful businessman and that he will run the country like one. But it's worth noting that Warren Buffett , a far, far more successful businessman than Donald Trump will ever be, has never publicly attacked a federal judge, has given vast sums to charity, and has even disclosed his tax returns although he has never run for office.

Don't-Disclose Donald, on the other hand, prefers to keep his money and his money-making tactics, like the scripts for Trump U or "The Apprentice," hidden in the shadows. That may or may not be good business. But it's definitely not good democracy.