Feinstein’s death should be more than startling. It should be a warning to the people in both parties who believe they can bend their own mortality to an electoral calendar or a personal timeline for legacy-building.

This delusion has never been more common or more potentially disruptive in the United States than it is today.

With the great probability that Joe Biden and Donald Trump will be nominated for president next year, it is not a leap to say that it is likelier now than at any other point in recent memory that the next American president will expire before his term does.

Biden’s age is a constant topic of conversation, but it is typically addressed in terms of electoral implications: Are voters really prepared to accept a president who would be 86 upon leaving office? Embedded in the question is a daring presumption about Biden’s lifespan.

The same could be said of Trump, the 77-year-old former president whose personal health is largely a question mark, and of Senate Minority Leader Mitch McConnell, the 81-year-old Republican who suffered a fall earlier this year and has frozen up twice on camera since July. McConnell has declined to answer detailed questions about his condition, explaining away his obvious struggles as a function of lightheadedness.

All these men seem to resent being reminded of their own mortality. The White House staff responds with snark and brittleness to coverage of the president’s age. McConnell is not an expressive man, but his irritation at being questioned about his health is readily apparent.

Trump has blustered his way through the age issue so far, but he has never given an honest accounting of his physical state. His struggle with a dire coronavirus infection at the end of the 2020 campaign — and his attempt to obscure the gravity of that illness — should be a cautionary tale for anyone who believes they can make a confident assessment of his physical robustness.

These are not cheap-shot political jibes. American politics is littered with examples of death intruding abruptly on our political leadership, changing the course of history in the process. Presidential assassinations to be sure, but also plane crashes and car wrecks and illnesses and other shootings.

Feinstein’s life was a prime example of this: She became mayor of San Francisco not by the ballot but by the bullet, after the murder of George Moscone in 1978. There is a painful irony now that someone else will ascend to high office not by choice of California voters but because Feinstein, too, has left a sudden vacancy for someone to fill.

Electoral politics is a contingent business and mortality is the ultimate contingency. The only mystery is how few senior statesmen and stateswomen seem to grasp this.

One person who must understand it is Biden, whose long life has been convulsed over and over by searing tragedy. If anyone in American politics knows that death keeps its own calendar, it is him. The president cannot be oblivious to the actuarial risks involved in seeking a second term — risks to himself, his party and the country.

But this is also part of why so many politicians cling to their positions well past the point that it is medically advisable. If leaving office means accepting the inevitability of death, then you can start to see the appeal of running again. And again. And again.