About a decade ago, my daughters and I had a delightful lunch with Dianne Feinstein, one of the US senators representing California. She was vibrant, funny, whip-smart and offered me sage advice about my career. “Pace yourself!” she urged, as we discussed the logistics of my life as a working mother with young children. She was every inch the pioneering icon who has paved the way for other women in American politics.

Today, at 90, Feinstein remains a senator. But after suffering health problems in recent years, she cuts an increasingly frail figure. Following her prolonged absence from the Senate earlier this year, Ro Khanna, a level-headed Democrat congressman from California, pleaded with her to resign before her term is up, so that she can “end [her] service with dignity”. I am told family members have made similar appeals. Feinstein refuses to retire.

Her situation is not a one-off. There is currently speculation about the health of Mitch McConnell, 81, the head Republican in the Senate, who has “frozen” twice during recent press conferences. Meanwhile, the age of President Joe Biden continues to be the focus of scrutiny. A new Washington Post poll shows that 74 per cent of voters consider Biden, who would be 82 at the start of a second term, too old to run for the White House again.