Many presidents, starting with Thomas Jefferson, have faced calls for impeachment. Most presidents and members of their administrations, starting with the presidency of George Washington, have come under fire for serious breaches of law and conduct. How can we understand our present crisis against the long record of presidential wrongdoing?

Until the presidency of Richard Nixon in the 1970s, White House misconduct flowed in expected human channels. From the start, greed proved the major motivation of those caught out for breaking the law. The first instance of executive branch malfeasance, which occurred in 1792, during Washington’s first term in office, involved the theft of federal funds by a well-known speculator serving as assistant secretary of the Treasury. Ever since, high federal officials have tried to use public office for private gain.

When faced with charges of misconduct, officials’ go-to defense has been to try to cover up their actions, whether it’s the misuse of government funds or sexual dalliances, the latter in the case of Bill Clinton and Donald Trump.

Lying, as Ronald Reagan did about his knowledge of the unlawful transfer of funds from one use to another during the Iran-Contra affair, has played a large role in coverups. Human embarrassment is a rich seedbed for attempts to suppress evidence.

But over 230 years of constitutional government, presidential misconduct has been forced often to change course. Laws that removed federal offices from patronage and outright purchase – the most famous example being Andrew Jackson’s “spoils system” – have made federal service more honest than it would have been without them. Where earlier it was relatively easy to award federal contracts to political friends – as was the case in the notorious Teapot Dome scandal of Warren Harding’s administration in the 1920s – the tightening of bidding rules has now made it difficult for federal officials to award contracts to political favorites.

More, of course, could be done. The Supreme Court gutted Congress’ efforts on campaign finance reform in its egregious Citizens United decision in 2010. Public offices and access to public officials, including presidents, are still for sale. It’s just that now you buy those privileges through campaign contributions rather than directly from federal officers.

Throughout the nation’s history, presidents and officials who stepped over the line of convention and law always faced the dangers of exposure and legal penalty. Existing laws, an aroused citizenry, a robust press, vigilant federal officials (now buttressed by the protections of whistleblower laws), congressional investigations and the courts have stepped in to call erring officials to account.

And yet such defenses against misconduct are never enough, as the record shows, to prevent all wrongdoing, especially when wrongdoing is orchestrated out of the White House and covered up there. That’s the novel situation that we’ve faced since Nixon’s presidency and face once again. And there’s probably nothing short of impeachment – what has been called “the grand inquest of the nation” – that can deal with it.

No president before Nixon used the Oval Office for illegal activity. Previous presidents facing charges of misconduct were often the victims of their own naïveté and the people they’d appointed to office. Ulysses S. Grant and Warren Harding, who presided over two of the most corrupt administrations in American history, were themselves blameless of misconduct. They simply couldn’t bring themselves to fire wrongdoers whom they happened foolishly to trust. But they didn’t engage in it themselves.

Nixon was different. As the Watergate tapes show, he waded into the fray with his close associates and approved, ordered and directed his administration’s coverups of its actions. For his involvement, he was named an unindicted co-conspirator in the Watergate burglary by a federal grand jury, the first chief executive ever to be so named.

That administration’s misdeeds ought to have served as fair warning to its successors. They appear not to have done so. President Trump has already been implicated as “Individual 1” in the criminal case against his former personal lawyer Michael Cohen. He has refused to cooperate with the House inquiry into his request that Ukraine investigate Joe Biden and his son and seems to be daring Congress to impeach him.

While freighted with danger, impeachment is the only instrument offered by the Constitution to bring an administration otherwise out of direct reach of the law to book.

No citizen can look upon the prospect of what’s ahead in the next few weeks with pleasure. But when what James Madison called “parchment barriers” – the Constitution, laws, court decisions, words on paper – no longer avail to discipline a president who defies the law, impeachment is the only option open to us.