President Biden is the oldest president in American history—at 78 years old when inaugurated, he was already older than previous record holder Ronald Reagan, who left office while still 77. Now Biden is reportedly planning to run for a second term. Sources tell The Hill that he has informed Barack Obama to this effect. If he wins and serves out another four years, he would be 86 at the end.

Now, this may not actually happen. The Hill is not exactly a reliable source, and it is generally politically unwise for a president to announce long in advance that they are not running for a second term even if that is the case, since it makes them a lame duck and sets off an instant succession scramble. But it is still indicative of a political party looking down the barrel of a huge power vacuum because its elderly leadership has not paved the way for any successors.

Biden is 79, but he is still younger than the entire House Democratic leadership. Speaker of the House Nancy Pelosi and Majority Leader Steny Hoyer are both 82, while Majority Whip Jim Clyburn is 81. Senate Majority Leader Chuck Schumer is a comparative spring chicken at just 71, though Senate Majority Whip Dick Durbin is 77. At 57, Vice President Kamala Harris is by far the youngest top-ranked Democrat, and she is still ten years older than Barack Obama was when he was inaugurated in 2009. As Christopher Ingraham points out, this makes the average age of the president and the leaders of the House and Senate higher than it has ever been in American history.

Worse, there is not even a middle-aged heir apparent for any of these positions. So far, reporting on Pelosi’s plans to retire has been contradictory, but if she does give up the speakership both her lieutenants will likely also quit, and it would be a succession free-for-all. Sen. Patty Murray (D-WA) is the likely successor to Schumer in the Senate, but she is just as old. Harris would take office if Biden were to die before his term was up, but if he does not run again, insiders are already predicting a bitter primary battle because her approval ratings are so soft—just under 40 percent approval in the FiveThirtyEight polling average, though to be fair Biden’s numbers are just as bad—and she has relatively little firm support in the Democratic establishment.

This is not to say that all politicians should be under, say, 60. Some people can and do function in top form long into their eighties, like West German Chancellor Konrad Adenauer, who expertly guided his country through the chaotic post–Second World War years. Moreover, a political party can benefit from a few graybeards to pass along political wisdom and institutional knowledge.

But it is one thing to have a single elderly leader, and quite another to have most of the top ranks of an entire political party composed of people well into their twilight years.

Moreover, high-functioning octogenarians like Adenauer tend to be the exception. Science tells us that as people age, they tend to lose cognitive capacity, particularly the ability to process new information quickly. The onset of serious cognitive decline can be quite fast, as well—witness Sen. Dianne Feinstein (D-CA), whose memory problems have been discussed for years and who now reportedly struggles sometimes even to remember the names of her own colleagues in the Senate.

A few bad rolls of the actuarial dice, and Democrats will be embroiled in an apocalyptic succession struggle—like when they lost a Supreme Court seat because Justice Ruth Bader Ginsburg refused suggestions to retire in 2013, when she had already had two exceptionally deadly cancers. Being a political leader is a difficult job, which is precisely why one of its most important tasks is preparing a second-in-command to take the reins.