A serious conversation about impeaching President Donald Trump is underway. But it may be going in the wrong direction already.

Even before Wednesday’s appointment of a special counsel to investigate ties between the Trump campaign and Russia as well as possible attempts to conceal them, lawyers were all over television arguing whether Trump’s actions to date constituted an “obstruction of justice” that would earn a conviction in a normal criminal proceeding. They particularly focused on the president’s reported request that former FBI Director James Comey drop an investigation into Trump’s former national security adviser, Michael Flynn.

But impeachment is not a normal criminal proceeding, and official constitutional grounds for removal go beyond whether a president has broken the law. On the contrary, the Constitution reserves impeachment and removal for instances of “Treason, Bribery, or other high Crimes and Misdemeanors.”

There’s a reason for that. The document’s framers weren’t out to punish crime when they wrote the impeachment clause. They were trying to construct a mechanism for removing a threat to democracy.

The question for Congress ― and eventually, the public ― is whether, given available evidence, Trump constitutes that kind of threat.

Impeachment is about protecting constitutional democracy.

The Constitution is reasonably specific about how Congress goes about removing a president. The process begins in the House, with the Judiciary Committee (or some other committee that Congress designates) drawing up articles of impeachment specifying the president’s alleged offenses. If the committee approves the articles, the full House considers them. On the floor, as in committee, a mere majority is sufficient for approval.

Such a vote ends the actual impeachment phase, which is roughly akin to an indictment. The question of whether to “convict” falls to the Senate, where deliberations can appear more judicial than political ― with the House sending over “managers” who serve the role of prosecutors, and the president sending his lawyers to defend him. The chief justice of the Supreme Court sits as the presiding officer, ruling on procedural matters, although the Senate can overrule the chief justice by majority vote.

Eventually, the Senate withdraws to closed session to deliberate, and then returns to vote in public, with a hefty two-thirds majority ― 67 senators, if the full Senate is present ― necessary to expel the president from office and power.

Yet the Constitution is a lot less specific about which transgressions actually warrant removal. Bribery and treason are clearly defined enough, but the phrase “high crimes and misdemeanors” is a different story.

The framers added the phrase to the impeachment clause at the Constitutional Convention, when George Mason feared that provisions against bribery and treason alone would not sufficiently contain a despotic executive, but James Madison thought Mason’s choice of phrase, “maladministration,” was overly broad.

“I take the idea to be that they wanted to deal with serious offenses against the state, not petty illegality,” Josh Chafetz, professor of law at Cornell, explained over email on Wednesday.

The point, Chafetz said, was to deal with transgressions that “had to do with aggrandizement of the office, trampling on norms of governance, etc. They didn’t have to do with contempt in a civil case, or other small-bore offenses that were largely unrelated to office.”

Clintonian and Nixonian offenses are different.

That standard prevailed in the late 1990s, during the impeachment of former President Bill Clinton. Nobody questioned that Clinton had broken the law when, during a deposition for a civil case, he lied under oath about his sexual relationship with a White House intern. He was guilty of perjury.

But after the House passed articles of impeachment, the Senate fell well short of impeaching Clinton, mainly because even Republicans came to agree with Democrats that he was not guilty of any offense that qualified as a “high crime.” He had lied to conceal the existence of a private relationship that many people thought should never have become public in the first place.

The circumstances were very different in 1974, when the House Judiciary Committee was preparing articles of impeachment for former President Richard Nixon. Over the course of two years, thanks to a combination of intrepid journalism and an aggressive special counsel, it became apparent that Nixon had conspired with his aides to cover up ― and then suppress the investigation of ― efforts to spy on and sabotage Democrats in the 1972 election.

A violation of the criminal law is neither necessary nor sufficient to make something a high crime or misdemeanor. Josh Chafetz, professor of law at Cornell

To this day, it remains unclear whether Nixon actually ordered the Watergate break-in that gave the scandal its name. (For a refresher, read Dylan Matthew’s comprehensive guide to Watergate at Vox.)

But recordings captured Nixon telling his aides he wanted the FBI to back off investigation of a crime ― and not just of any crime, but of an attempt to tamper with a presidential election. They were also evidence that Nixon was using his control of federal law enforcement to shield himself and his associates from accountability.

This week’s New York Times revelation ― that Comey has a memo, written contemporaneously, about Trump urging him to back off the Flynn investigation ― suggests Trump may have engaged in behavior strikingly similar to Nixon’s, although he has denied wrongdoing. More such evidence may emerge, whether through congressional testimony or the special counsel investigation now getting underway.

It still might not be enough to win a conviction in court, given the technical definition of “obstruction of justice” and how it would apply to the president, who occupies a unique position overseeing federal law enforcement. But, as Harvard Law Professor Noah Feldman wrote this week at Bloomberg View, it could still be an “obvious and egregious abuse of power” ― the kind that would have eventually led to Nixon’s removal from office, had he not resigned first.

“A violation of the criminal law is neither necessary nor sufficient to make something a high crime or misdemeanor for impeachment purposes,” he said. A small crime is not automatically an impeachable offense, he argued. Alternately, he said, someone could do something immoral that, while technically legal, could disqualify them from staying in office.

Impeachment always comes down to politics.

In the end, it wasn’t principle that drove Nixon from the presidency. It was politics. He resisted resignation as long as he could, relenting only when a group of loyal Republicans told him, in person, he didn’t have the votes to survive the coming impeachment proceedings.

And so it will be now. Trump’s ability to survive the coming investigation and what it produces will ultimately depend on whether Republicans are willing to stand by him.

So far, by and large, they have ― shielding him from inquiries on everything from Russia to his tax returns ― perhaps because they believe his continued presence in the White House offers their best opportunity to pass their legislative agenda, or perhaps because they are not yet ready to openly challenge a party leader who retains the enthusiastic support of so many Republican voters.

For better or worse, this, too, is how the framers wanted it.

“The trappings of legality serve to discipline the proceedings and to prevent them from becoming merely a tool of partisan warfare,” Nicholas Bagley, law professor at the University of Michigan, said on Wednesday. “At the same time, the House and the Senate ― not judges ― are charged with carrying out this judicial-style process. The Constitution’s drafters knew that political considerations would influence legislators’ judgments. The open-endedness of the ‘high crimes and misdemeanors’ phrase affords legislators a lot of room to designate those offenses that, under the circumstances, warrant impeachment.”

Of course, political conditions change. If the special counsel produces even more powerful evidence of Trump’s wrongdoing, public outrage might become too overwhelming for this Republican Congress to ignore.

But a lot depends on whether the conversation about Trump’s future in office focuses on the right question: whether, through his actions, he has seriously undermined the rule of law or democratic process.