An impeachment process against President Trump now seems inescapable. Unless the president resigns, the pressure by the public on the Democratic leaders to begin an impeachment process next year will only increase. Too many people think in terms of stasis: How things are is how they will remain. They don’t take into account that opinion moves with events.

Whether or not there’s already enough evidence to impeach Mr. Trump — I think there is — we will learn what the special counsel, Robert Mueller, has found, even if his investigation is cut short. A significant number of Republican candidates didn’t want to run with Mr. Trump in the midterms, and the results of those elections didn’t exactly strengthen his standing within his party. His political status, weak for some time, is now hurtling downhill.

The midterms were followed by new revelations in criminal investigations of once-close advisers as well as new scandals involving Mr. Trump himself. The odor of personal corruption on the president’s part — perhaps affecting his foreign policy — grew stronger. Then the events of the past several days — the president’s precipitous decision to pull American troops out of Syria, Secretary of Defense Jim Mattis’s abrupt resignation, the swoon in the stock market, the pointless shutdown of parts of the government — instilled a new sense of alarm among many Republicans.

The word “impeachment” has been thrown around with abandon. The frivolous impeachment of President Bill Clinton helped to define it as a form of political revenge. But it is far more important and serious than that: It has a critical role in the functioning of our democracy.