President Trump’s firing of FBI Director James Comey has set off a lively debate over whether the move amounts to a “constitutional crisis.” On the one hand, there is little doubt that Trump had the legal authority to oust Comey. On the other hand, the firing may have violated norms of judicial independence: Comey was overseeing an investigation into whether members of Trump’s team had connections to Russian efforts to interfere in last year’s presidential election. There is fairly wide agreement among scholars that this week’s news raises serious questions about abuse of power and the rule of law; there is much less agreement as to whether it is a constitutional crisis, per se.

Complicating the debate is the fact that there is no single, clear definition of what a constitutional crisis even is. Back in February — the last time the phrase “constitutional crisis” was making headlines — we identified four different types of crises. They were, in brief:

The Constitution doesn’t say what to do: Something happens for which the Constitution doesn’t provide instructions.

Something happens for which the Constitution doesn’t provide instructions. The Constitution’s meaning is in question: The text offers conflicting possibilities or throws up a phrase like “high crimes and misdemeanors” or “commerce among the states” that invites different interpretations.

The text offers conflicting possibilities or throws up a phrase like “high crimes and misdemeanors” or “commerce among the states” that invites different interpretations. The Constitution tells us what to do, but it’s not politically feasible: Like having the House of Representatives decide the 2000 election.

Like having the House of Representatives decide the 2000 election. The institutions themselves fail: Congress, the president, the courts and the states are all supposed to check each other in order to uphold the Constitution. But they don’t always do what they’re supposed to.

Comey’s firing doesn’t fall neatly into any one of these buckets, but it has elements of at least three of them. Let’s go through them quickly:

Institutional failure

Almost as soon as Comey’s firing was announced, commentators started comparing the move to the “Saturday Night Massacre” in 1973, in which President Richard Nixon ordered the firing of Archibald Cox, the special prosecutor investigating the Watergate break-in. There are some clear, surface-level similarities between the two incidents, which both involved the ouster of officials investigating the White House. But there are also key differences. In 1973, the attorney general and deputy attorney general both resigned rather than carry out Nixon’s order. (Solicitor General Robert Bork, who took over the Justice Department, then fired Cox.) This week, by contrast, Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein cooperated with Trump; Rosenstein wrote a memo outlining the case against Comey (although it stopped short of calling for his ouster), and Sessions wrote a letter to Trump calling for his firing. Trump has since said that he had already decided to fire Comey, and did so for reasons unrelated to the justification laid out in Rosenstein’s memo. Rosenstein and Sessions, therefore, appear to have provided Trump a pretext for a decision he planned to make anyway.

The Constitution isn’t very specific about how each of these institutions — the White House and the Department of Justice — is supposed to behave, especially when the latter is investigating the former. But if the White House is interfering with a federal investigation, that certainly seems like an institutional failure. The institution designed to oversee the White House to mitigate such abuses, Congress, also has seemed very reticent to do that job so far — another form of failure. This touches on the next form of crisis:

Constitution says what to do but it’s not politically feasible

The system of checks and balances we all learned about in grade school isn’t explicitly discussed in the Constitution, but the idea that the branches of government are meant to help keep each other in check is still a bedrock principle of the U.S. system of government. James Madison, writing in Federalist 51, explained that, “Ambition should be made to counteract ambition.”

That’s not how things are working in the federal government right now. Congressional Republicans have mostly stayed quiet, or expressed “reservations” in a noncommittal way. They have very understandable electoral incentives for behaving this way, but if those political considerations prevent them from performing a vital constitutional job — overseeing the executive branch and investigating presidential abuses of power — this is a form of crisis.

The Constitution doesn’t say what to do; or

The Constitution’s meaning is in question

We’ll take these two categories together. One of the most important provisions of Article II (the one that sets up what presidents do) is the “take care” clause, which obligates the president to execute the laws and uphold the Constitution. Article II also places the president in charge of the executive branch, which puts firing Comey squarely within his authority.

What the text does not clarify is what happens when these duties come into conflict. In the past, the obligation to protect the laws and Constitution has been used to justify expansive executive action, from Lincoln’s suspension of habeas corpus during the Civil War to claims of “executive privilege” by virtually every modern president. This doesn’t mean presidents can do whatever they want in the name of enforcing the law — courts have certainly pushed back against executive privilege at times. But a growing number of observers have expressed concern that Trump’s actions subvert the rule of law and may have enabled a foreign country to interfere in a U.S. election without consequences. The Constitution puts the president in charge of executing the laws, and when that doesn’t happen, it’s expected that Congress will step in. But the text is quite vague about what members of Congress should do — or what will happen if they don’t act.

The term “constitutional crisis” is a slippery and overused one. Quite often, the Constitution offers us a roadmap for addressing transgressions. The Civil War was a true constitutional crisis because there was substantial disagreement over a basic aspect of the national compact (Could states leave?) and the two disagreeing sides were each well-armed and convinced of their rectitude. But to call a presidential abuse of power a crisis of the constitutional system is like calling a bank robbery a crisis of the financial system. It’s not. There are ways to address it.

The problem comes when the relevant actors simply won’t perform their constitutional duties because of other considerations. Trump has violated all manner of norms in the early months of his presidency — he hasn’t divested from his business interests, his daughter has a West Wing office, her husband represents the nation abroad, he falsely accuses his predecessor of crimes, he conducts foreign policy outdoors at a restaurant and using unsecured phones, etc. — and those violations have largely gone unaddressed by one of the two branches of government in charge of regulating him. (The judicial branch, of course, has been a consistent thorn in Trump’s side.) But we face new norm violations today, including the president’s threatening the former FBI director over Twitter.

If Congress continues its investigation into Russian interference in the election and assures that the FBI does the same, then the Constitution’s checks and balances could end up working. (That investigation could, of course, lead to another kind of crisis, depending on what it concluded.) But if Trump continues to interfere in the FBI’s activity, and Congress doesn’t step up its own investigation, we could end up in a true constitutional crisis.