For scholars of democracy who have kept anxious watch over the tumultuous first months of this presidency, this week’s firing of James Comey set off a new round of alarm bells.

As President Trump attacked judges, intelligence agencies, the press, even the Congressional Budget Office — all potential independent constraints on presidential power — they constantly adjusted their scorecards, trying to sift the alarming from the merely noisy. But firing the official who heads an investigation into possible collusion between a presidential campaign and a foreign power crossed a line, they agreed.

“My alarm-o-meter definitely jumped,” said Lee Drutman, a senior fellow at the New America Foundation. “I’d say I went from a 4 to a 7 out of 10.”

Few argue that the United States is in imminent danger of becoming an autocracy, a term much chewed over by pundits these days, including some conservative ones like David Frum, President George W. Bush’s former speechwriter. But in conversations over the past few months, scholars’ moods and assessments have soared and plummeted.