The Trump era demands a re-examination of some basic questions that we might have thought were settled. And here’s one that may well one day become an urgent matter: What’s a high crime or misdemeanor?

The Constitution, as we all know, doesn’t define the phrase. The language in Article II, Section 4 refers to “Treason, Bribery, or other High Crimes or Misdemeanors.” And usually, that’s how we think about the definition of the key phrase. Serious, Nixon-level corruption and illegality.

But the combination of reading recently about the impeachment of Andrew Johnson and watching Donald Trump’s horrifying press conference last week about Charlottesville got me wondering: Is espousal of un-American beliefs an impeachable offense in a president? And if not, why not?

Bear with me—the answer is less cut-and-dried than you think it is, and I have a few constitutional scholars backing me up here.

First, a bit on Johnson. He was Lincoln’s vice president, as you know, but a Southern Democrat, chosen by Abe for an 1864 national unity ticket. He was not a secessionist but was definitely a racist. As president after Lincoln’s assassination, he got into huge fights with the Republican-controlled Congress over Reconstruction: how amnesty should be granted to ex-Confederates, what seceding states would have to do to get back in the Union, and so on. To make a long story short, Congress passed a law forbidding him from firing his pro-Reconstruction secretary of war. He promptly turned around and did exactly that. Impeachment began immediately. The House passed charges, but the Senate failed to convict by one vote.

Johnson was impeached, in other words, over political disagreements with Congress. Very intense ones, resulting in the most vetoes and overrides of those vetoes of any president, and culminating in his use of the Union army to defy Congress’ wishes. But ideological disagreements all the same. Historians have generally judged the Johnson impeachment to have been unjustified because what he was doing, however objectionable from a moral point of view (i.e., imposing policies that upheld racism), broke no laws.

So that’s one extreme. At the other sits Nixon, whose offenses, nearly everyone agrees, were criminal and worthy of removal.

And that’s how impeachment conversations tend to be framed: either Nixon or Johnson. Yes, there’s Bill Clinton, but that was nonsense—revenge for Nixon, basically. No reasonable person who wasn’t already ideologically committed to Clinton-hating thought that lying under oath about a legal (however distasteful) act was an impeachable offense, which helps explain why Clinton not only survived but saw around 65 percent of Americans approve of his performance of president as it played out.

But what if there’s space between Nixon and Johnson? This is the question that occurred to me as I watched our president, the president of the United States, speak last week of a moral equivalence between neo-Nazis and people protesting neo-Nazis.

What if a president espouses views that are so plainly un-American, so clearly at odds with American creedal belief, that they constitute not mere political disagreement but something that is at war (as Steve Bannon might put it) with the values embedded in the Constitution?

Let’s imagine an extreme hypothetical. Say a president takes office and installs a bust of Hitler in the Oval Office and starts quoting from Mein Kampf. Or does the same with Stalin, or Mao. Americans would be horrified; surely (hopefully!) 97 percent of the people would instantly decide that this man should not be the president. Would Congress be within its rights to start impeachment proceedings against this president?

I asked six constitutional experts what they thought, and four said, to varying degrees, that this could constitute legitimate impeachment grounds.

Here’s Bruce Fein, the conservative legal scholar who worked in the Reagan administration: “I think the mere holding of beliefs as an academic matter would not be impeachable. But if the president advocated or endorsed the beliefs of Mao, Hitler, Stalin, Mussolini or other notorious tyrants through words or body language or otherwise, the advocacy or endorsement would conflict with the presidential oath of office in Article II to ‘preserve, protect, and defend the Constitution of the United States.’ The president would be sabotaging, not defending the Constitution—including its separation of powers, due process, and equal protection—by applauding the ideas or actions of tyrants from his bully pulpit. Indeed, the Declaration of Independence posits that citizens are saddled with a ‘duty’ to overthrow tyranny.”

Next up Sanford Levinson, liberal, of the University of Texas School of Law. Levinson is a noted critic of the Constitution. “ Gerald Ford in 1971 (in)famously said that an impeachable offense is whatever a majority of the House of Representatives says it is,” he wrote to me last week. “So why shouldn’t a majority of Republicans and Democrats alike declare that Donald Trump has so blasphemed the American civil religion as set out in the Preamble and such statements as the Gettysburg Address or Martin Luther King’s ‘I Have a Dream’ speech that he deserves to be fired? And perhaps two-thirds of the Senate would agree? But we should recognize that this is a decidedly inadequate way to get rid of a president who might truly be a menace to everything this country stands for.” He would like to see two-thirds of Congress be able to remove a president via a no-confidence vote.

Akhil Reed Amar of Yale Law School said: “The head of state is the embodiment of the nation. When he defies bedrock propositions of the American creed, if he doesn’t understand that basic creed, that might be grounds for impeachment. But—Republicans have to say it. Not we who voted against him. The people who have to undo the mandate are the people who gave him the mandate.”

Eric Posner of the University of Chicago Law School thought such a case is potentially valid, but more so if the president concealed his real ideology during the campaign. “Well you don’t necessarily need a traditional crime,” Posner emailed me. “A president could be impeached for staying in the basement and not running the government. Your case is more complicated. I think Congress could impeach, say, a mole. But not sure this would make sense if voters knew of or suspected the president’s real ideology.”

Two scholars I asked, Erwin Chemerinsky of Berkeley and Bruce Ackerman of Yale, took the more traditional view of impeachment.

Chemerinsky: “In one sense, high crimes and misdemeanors means whatever a majority of the House and two-thirds of the Senate says it means. On the other hand, I think that it clearly connotes an abuse of power. Espousing un-American views is not enough for that.”

And Ackerman: “Impeachment should be reserved for cases in which presidential conduct breaks fundamental constitutional limits. Impeachment for mere belief creates a precedent that would transform it into a ‘vote of no confidence’ device, generating deep pathologies, given the evolution of Congress.”

I’m not saying we’ve reached that point with Donald Trump. I don’t think we have. We don’t know for sure, for example, that he is a white supremacist. But what’s disturbing is that we don’t know that he isn’t. He sure sounded pretty close to one last week at Trump Tower, when he was obviously telling us how he really felt about Charlottesville.

And what if after a few more of these episodes it becomes undeniably apparent to just about everyone that we have a racist in the White House? We’ve had them before, and not just Johnson. But that was when such views were widely held, accepted, and (in a number of places and/or ways) legal. Now, racism is very clearly understood to be un- and anti-American.

In terms of removing a president, there’s also the 25 th Amendment solution, but that’s a higher bar than impeachment, since it involves both Congress and Cabinet members. Besides, the fact is that “we the people” theoretically have our will expressed by Congress. Should the people’s representatives tolerate a racist president because he’s broken no criminal laws?

I see the dangers that lurk in asserting such a standard. But if you don’t see the danger in not asserting one, you haven’t been paying much attention to this man and his lack of compunction about tearing this nation in two.