Democracies used to collapse suddenly, with tanks rolling noisily toward the presidential palace. In the 21st century, however, the process is usually subtler.

Authoritarianism is on the march across much of the world, but its advance tends to be relatively quiet and gradual, so that it’s hard to point to a single moment and say, this is the day democracy ended. You just wake up one morning and realize that it’s gone.

In their 2018 book “How Democracies Die,” the political scientists Steven Levitsky and Daniel Ziblatt documented how this process has played out in many countries, from Vladimir Putin’s Russia, to Recep Tayyip Erdogan’s Turkey, to Viktor Orban’s Hungary. Bit by bit the guardrails of democracy were torn down, as institutions meant to serve the public became tools of the ruling party, then were weaponized to punish and intimidate that party’s opponents. On paper these countries are still democracies; in practice they have become one-party regimes.

And the events of the past week have demonstrated how this can happen right here in America.

At first Sharpiegate, Donald Trump’s inability to admit that he misstated a weather projection by claiming that Alabama was at risk from Hurricane Dorian, was kind of funny, even though it was also scary — it’s not reassuring when the president of the United States can’t face reality. But it stopped being any kind of joke on Friday, when the National Oceanic and Atmospheric Administration issued a statement falsely backing up Trump’s claim that it had warned about an Alabama threat.