Former President Richard Nixon released his tax returns during a public scandal to try and prove he wasn't a crook.

While President Trump has still not released his returns, the recent New York Times investigation revealed some of the "tax schemes" committed by Trump's father.

Both cases have similarities and show how the manipulation of the tax system by high-ranking US politicians affects voters.

Richard Nixon released his tax returns to try and prove he wasn't a crook. It didn't work out, quite — the numbers showed he'd taken big deductions that looked bad in the light of day.

Jimmy Carter released his full tax returns to bolster his image as a plain man of the people. They revealed his biggest assets as a family peanut business and a small amount of stock, both of which he put in blind trusts when he won.

George H.W. Bush released his tax returns because that was the political norm by the time he became president. They showed he was rich — but also generous, as he and first lady Barbara Bush donated 62% of their $1.3 million income to charity in 1991.

How presidents treat their tax obligations as citizens can symbolize their character and their attitudes toward the business of American government as a whole.

It is also something voters — taxpayers themselves — watch critically, and can relate to and understand. After all, the entire United States tax system rests crucially on self-assessments. Few returns are audited. Most Americans are willing to pay their fair share if they think others are (roughly) paying a fair share too.

Historically, the high-water mark for American dissatisfaction with government was the 1970s — the era of Vietnam, Nixon and Watergate. John Duricka/AP

Blatant tax cheating at the top can collapse this agreement. Look at Greece, where widespread political corruption has fed a culture of tax avoidance that costs the government revenues equal to 6 to 9% of the country's gross domestic product.

This is the context for The New York Times' massive investigation of the "tax schemes" President Trump participated in during the 1990s — actions that included instances of "outright fraud," and greatly increased the fortune Mr. Trump received from his parents, according to the Times.

Read more: The creative accounting that reportedly allowed Jared Kushner to dodge paying income taxes for years is totally legal

According to John Dean, who was Nixon's White House counsel and is now often critical of Trump, it may take a while for the details of the Times report to register with voters, but it won't be good for the president when they do.

"Nixon did not have Trump's wealth but most Americans felt his tax cheating was bad... Few Americans want a tax cheat as President," Mr. Dean tweeted in the wake of the Times report.

Nixon's experience is in fact a good case study in the reaction of voters to perceived manipulation of the tax system by high-ranking US politicians.

In November 1973, Nixon was trying to get the press off the developing Watergate scandal and the "Saturday Night Massacre" of October 20, in which the president fired special prosecutor Archibald Cox and the attorney general and deputy attorney general resigned rather than be parties to that action.

Some limited candor might help, Nixon and his advisers thought. So on November 17, 1973, the president held a question-and-answer session with newspaper editors at Disney World. Dogged by queries about his personal finances, Nixon fought back, saying he'd earned every cent received in public service.

"People have got to know whether or not their president is a crook. Well, I am not a crook," Nixon said.

Trump holds an example of what a new tax form may look like during a meeting on tax policy with Republican lawmakers in November 2017. Evan Vucci/AP

Days later he released his tax returns to try and prove this point. The documents did quiet some of the wilder charges against him, such as questions about the financing of his houses and suspicion that he was financially tied to billionaire Howard Hughes.

But they showed that Nixon had made aggressive use of deductions, and paid relatively little in income taxes. In particular, Nixon had claimed a $576,000 deduction based on the perceived value of a charitable donation of his vice-presidential papers.

The deduction itself was legal at the time — Dwight Eisenhower had taken a similar course of action. But Nixon had wrongly backdated the timing of the donation. An investigation showed he owed a considerable amount in back taxes, which he paid.

Nixon lost the presidency because of his actions regarding Watergate. But the tax issue left a stain he couldn't scrub off.

"Make sure you pay your taxes. Otherwise you can get in a lot of trouble," he told journalist David Frost in one of their famous post-presidency interviews.

Read more: How Democrats could make Trump's tax returns public

As for Trump, the tax issues involved are more complicated, and involve far larger sums of money. No president has been as wealthy as Trump. For that reason alone, the Times investigation is in unexplored American territory.

The paper describes some of the moves to evade estate taxes as "fraud." Other aspects of Trump's taxes might just be aggressive moves typical of wealthy Americans. As the response by Trump's lawyer has noted, the Internal Revenue Service appears to have approved all Trump family tax returns at the time.

The most stinging aspect of the report, for the president, might be its assertion that he received at least $413 million from his father's real estate empire over the years — calling into question his personal branding as a self-made building baron.