When news broke that Donald Trump had fired James Comey, who was in the midst of investigating possible collusion between the Russian government and the president’s campaign, Brian Schatz knew just what to call it. “We are in a full-fledged constitutional crisis,” the Democratic senator wrote on Twitter. A host of Democratic lawmakers have since echoed Schatz’s dire warning.

Are they right? And how would Americans know if they were living through a constitutional crisis? In a 2009 paper defining the term, the legal scholars Sanford Levinson and Jack Balkin noted that Americans have long overused the phrase, which isn’t surprising in a country tested to its core by a failed constitution (the Articles of Confederation), civil war, economic depression, and two world wars. In recent years, “constitutional crises” have been spotted in everything from the disputed 2000 presidential election to the failure of Congress to increase pay for federal judges. (For the record, Levinson and Balkin consider the 2000 election a “constitutional showdown” rather than a crisis, and the complaint about judicial salaries a “plaintive cry.”) Well before the firing of James Comey, Trump’s business conflicts of interest and battle with the courts over his travel ban sparked chatter about a looming constitutional crisis.

“People generally use the term ‘constitutional crisis’ to describe periods when institutions of government are clearly in conflict,” Levinson and Balkin wrote. “But the mere existence of conflict, even profound conflict, cannot be the definition of crisis. … Conflict in a constitutional system is not a bug—it is a feature.”

Levinson and Balkin also make a distinction between “political” and “constitutional” crises, arguing that the Watergate scandal and the impeachment of Bill Clinton are best described as the former. Richard Nixon, for example, arguably had the authority to fire the Watergate special prosecutor and eventually complied with a Supreme Court order to hand over the Watergate tapes. “Nevertheless, it could easily have become a constitutional crisis at several points if Nixon had publicly stated (which he never did during his presidency) that he sought deliberately to go beyond his powers under the Constitution,” they explained.

Constitutional crises, Levinson and Balkin wrote, should be understood “not in terms of constitutional disagreement but in terms of constitutional design.” And there are three types of design failure:

1) Political leaders flagrantly violate the constitution, typically justifying the power grab as a response to an emergency that the constitution isn’t designed to address.

2) Political leaders faithfully follow constitutional provisions even though the provisions are badly designed, leading to disaster or political paralysis.

3) People or government institutions disagree so intensely on how to interpret the constitution that the struggle surpasses ordinary political conflict; the government might, for instance, use force to stifle mass protests.

Comey’s dismissal is not a constitutional crisis, argued Steve Levitsky, a professor of government at Harvard who recently co-authored an article in Foreign Affairs on why American democracy could erode during Donald Trump’s presidency. “Trump was completely within his constitutional bounds in doing what he did.”

When Ecuadorean President Rafael Correa effectively fired 57 opposition lawmakers, when judges loyal to Venezuelan President Nicolas Maduro stripped the country’s legislature of its powers, when former Peruvian President Alberto Fujimori wiped out rival branches of government—these were genuine constitutional crises, Levitsky, who specializes in comparative Latin American politics, told me.

Such clear-cut constitutional crises are the exception, however, according to Gretchen Helmke, a political scientist at the University of Rochester and co-director of the democracy-monitoring group Bright Line Watch. The recent impeachment of Brazilian President Dilma Rousseff, for example, was considered a subversion of democracy by her supporters and a sign of a well-functioning democracy by her critics—a situation that might have resulted in a Type 3 constitutional crisis had the standoff escalated.

What the United States is experiencing this week could be characterized as a “political crisis,” Levitsky said. It “could make a constitutional crisis more likely in the future.” But more significantly, Trump’s action violated a pair of important but informal democratic norms in the United States, he argued.

In ousting Comey for apparent political reasons—whether related to Comey’s probes into Hillary Clinton’s emails or Russia’s interference in the 2016 election—Trump disregarded the norm of American presidents allowing the FBI director to complete his or her full 10-year term (since 10-year terms for directors were instituted in 1976, only one other FBI director has been fired, over ethics violations). This standard practice, Levitsky said, is intended to maintain the FBI’s status as a “powerful, independent agency capable of seriously investigating the government itself, the president himself.”

“I would not classify firing Comey as a constitutional crisis,” Helmke, who has studied constitutional crises in Latin America, wrote by email. “But given that Comey was leading up the investigation into the Trump campaign’s ties with Russia it is certainly deeply troubling in the larger sense of violating core principles of the rule of law. ... Trump acted within the letter of the law in terms of firing Comey. But if he then replaces him with someone who is seen as too close to the administration and the investigation is dropped, then the basic principle of ‘no one being a judge in their own cause’ will have been severely compromised.”

Trump, Levitsky added, also contravened a norm of “partisan restraint—that you do not use your institutional power to the max in order to ... gain unfair advantage over [rivals]. You underutilize your power in order to preserve democratic institutions.” A party with a majority in the House of Representatives, for instance, doesn’t impeach the president just because he’s an opponent, even though it technically could. A party with a majority in the Senate doesn’t block every Supreme Court nominee by a rival president. Or at least that used to be the case: Senate Republicans’ refusal to consider Merrick Garland, Barack Obama’s nominee for the Supreme Court, was a break with this tradition of restraint. And Trump’s dismissal of Comey, who was presiding over a Russia probe that Democrats zealously support, is another.

These norms are endangered in the United States because of factors that predate Trump and that will persist after he leaves office, Levitsky told me, including growing partisanship and political polarization in recent decades. “The more that I’m terrified or threatened by the other party, the more likely I am to justify breaking the norms, even breaking the rules in order to keep [the other party] from winning,” he said. (So far, many Republicans are defending Trump’s decision on Comey and rejecting calls for a special prosecutor to investigate Russian meddling in the election.)

But Trump may also accelerate the demise of certain American democratic norms. “He is a potentially authoritarian figure,” Levitsky said. “He’s shown that over and over and over again. We have, for one of the few times in our modern history, a guy in the Oval Office who’s not firmly committed to democratic rules of the game.”

Democratic norms are not inherently good or bad, according to Levitsky. They are meant to preserve political systems. Many of Trump’s supporters would likely applaud the president for defying norms that protect what they view as a corrupt, unresponsive, and undemocratic political establishment.

Yet liberal democracy, as practiced in the Western world, “is a set of formal constitutional [rules] and informal rules that constrain power—that make it hard to win power and carry out sweeping change,” Levitsky said. While U.S. democracy isn’t in “imminent danger of breakdown,” Levitsky’s research on how democracies collapse has revealed a pattern, which holds true from 1930s Spain prior to the rise of dictator Francisco Franco to 1970s Chile prior to the rise of dictator Augusto Pinochet.

Democratic breakdown is preceded by “the erosion of two key democratic norms: One, of restraint, of underutilizing power, not using your control over institutions to bludgeon your opponent to death. And secondly, what we call a ‘norm of legitimate opposition,’ which is viewing your partisan rival as fully legitimate—accepting that as much as you disagree with them, as much as you hate them, as much as you curse the heavens when they win the election, you accept that they’re not criminal, they’re not subversive, they’re not terrorists, they’re not a threat to national security, they’re not a threat to your way of life.”

“Norms of restraint and legitimate opposition serve as … the soft guardrails of democracy.” Levitsky said. “They prevent partisan competition from spiraling out of control.”

The firing of James Comey doesn’t make America a lawless banana republic. It doesn’t mean the United States has become Nicaragua. “This is the kind of thing that goes on in non-democracies,” the legal analyst Jeffrey Toobin declared on Tuesday night. But Toobin has it backwards: Trump’s move is consequential precisely because it’s going on in a democracy. It would have been more accurate for Brian Schatz to tweet, “We are witnessing the violation of unwritten, rarely tested norms that will further degrade the safeguards of American democracy.” Not a “constitutional crisis,” and certainly not a good tweet, but plenty scary as is.