The infirmities of aging have been much debated as they apply to recent presidents, but mostly ignored when it comes to the U.S. Senate, where there’s evidence of actual disability.

The most prominent example is Diane Feinstein, the California Democrat who made the apparently unwise decision to run for reelection in 2018 to a fifth full term at age 85.

Though Feinstein has had notable achievements during her 30 years as a senator, her physical and mental limitations have become so significant she can hardly perform her duties at even a modest level.

After a widely criticized performance during the first Trump impeachment, she stepped down as chair of the Judiciary Committee, but remains on the committee, and her long absences have delayed crucial appointments and legislation.

Yet hardly a word is uttered by colleagues, who behave as if being a U.S. senator is, like the Supreme Court, a lifetime appointment. It is not.

Majority Leader Chuck Schumer, a relatively youthful 72, has been solicitous of Feinstein to the point of obsequiousness, never even hinting, publicly or apparently privately, that it’s time to go.

Matters may have worsened when Feinstein’s husband, Richard Blum, died last year, leaving no family member to provide counsel. Instead, Feinstein and her daughter, to whom she gave power of attorney, are suing Blum’s children over his estate.

There are three powerful California congressmen running for Feinstein’s seat in 2024, some announcing even before she withdrew; her staff had to coach her to utter the words.

A short-term successor who’s not a candidate is the obvious answer — there is precedent — yet no one seems able to speak the words. California, and the nation, deserve a fully functioning senator.

Democrats are not the only party with a problem, however. There is, most notably, Mitch McConnell, the minority leader who’s been in a top leadership post for 20 years and, at 81, is serving his seventh term.

His colleagues have had difficulty communicating with him due to his hearing loss, and there was an alarming 20-second “freeze up” at a recent press briefing after which he was escorted away from the podium. A serious fall at the Trump Hotel ­— of all places; McConnell is not a fan — also roused concern.

McConnell’s actual health status is undisclosed, unlike President Biden’s, about which we get at least annual updates.

The minority leader does not brook opposition. Consider the fate of Rick Scott, the Florida senator who challenged him for the leadership post in 2022 after serving as Republican Party chair; almost nothing has been heard of him since.

But McConnell has ignored a problem that’s now reached scandalous proportions — namely the blocking of Defense Department nominations by Alabama Sen. Tommy Tuberville, who serves on the Armed Services Committee, including, ironically, subcommittees on Strategic Forces and Readiness and Management Support.

A dubious feature of Senate rules is that any senator can put an indefinite hold on a nomination. This “deliberative” feature has been abused before, but never on this scale.

Tuberville is now “holding” more than 300 nominees, including three of the eight members of the Joint Chiefs of Staff — the chief of Naval Operations, Army chief of staff, and Marine Corps commandant.

The senator’s beef is that the Pentagon, in accord with longstanding policy, is paying for service members to obtain abortions elsewhere if their home state now bars them. It’s difficult to see what other policy could have been adopted amid the chaos following the Dobbs decision, but to Tuberville, it’s the only issue that matters.

Thus a junior senator who’s been in office just two years is carrying out a one-man crusade with the acquiescence of his party’s leader, who’s been in the Senate since 1984. For good measure, Tuberville reportedly doesn’t even live in Alabama but in neighboring Florida.

McConnell’s silences about Donald Trump could been seen as strategic, given the state of his party. His silence about Tuberville is something else entirely.

This much seems clear: The Pentagon, rightly, is not going to change its policy, and Tuberville’s blockade has already lasted many months.

At a time when the United States is leading a coalition supporting Ukraine in its attempt to reverse Vladimir Putin’s autocratic invasion, this is unconscionable.

The Republican Party once made almost a fetish of “supporting the troops,” roundly criticizing any Democrat questioning a Defense budget item. Yet today’s troops can’t perform their duties without leaders.

If McConnell needs advice himself, he’d do well to heed the famous sign on Harry Truman’s desk in the Oval Office: The buck stops here.