Inner circle First lady and advisers have president's ear - but would he listen?

In March 1968, President Lyndon Johnson abandoned his re-election bid, citing the "awesome duties of this office", partisan divisions in the country, and "America's sons in the fields far away" in Vietnam.

- Edward Helmore

"I shall not seek, and will not accept, the nomination of my party for another termas your president," Johnson said.

It was a remarkable moment, recalls Hank Sheinkopf, a veteran Democratic political consultant: "No one gives up being the most powerful person in the world. It just doesn't happen."

LBJ was an exception, Sheinkopf says, in part because of his wife. Lady Bird Johnson "was not wild about the idea of becoming a political spouse", her biographer Julia Sweig wrote.

Yesterday, as the White House mounted a push-back against calls for Joe Biden to abandon his re-election bid, there is a dawning reality that despite Biden's catastrophic debate performance the night before, the decision to step aside or remain and potentially go on to a catastrophic defeat is his to make, and his alone.