It is a morbid element of journalistic paranoia, only inflamed in the past four years. Macabre and inhuman as it might sound, every foreign correspondent in the US (or every voter, for that matter) would surely admit the thought has at some stage crossed his or her mind. Will the President survive his term? Where and how would it happen? What would happen in the aftermath? How on earth would the world react?
Lincoln, Garfield, McKinley and Kennedy. There's good reason President Obama's victory speech was delivered behind walls of bulletproof glass.
It is most unlike the Catholic Church, of course, to ever be considered at all behind the times. What a relief, therefore, for the Pope to join the norm of most political positions of power, in relinquishing top office before slipping off to the other side. It just tends to make transitions a little tidier.
Eight US Presidents have died while still in office, and Barack Obama at least appears to take practical steps to avoid a premature departure. We're told he exercises regularly and at every speech or photo-op his appearance is pre-empted by scores of Secret Service agents, armed and utterly humourless. Rumours abound Obama even occasionally dresses in specially tailored, bullet-resistant clothing.
But the importance or not of a President lasting his term has been emphasised this week, not just by the Pope's premature passing of power (not to be confused with his premature passing), but by an off-hand comment from the former White House doctor, who served sitting presidents. Dr Connie Mariano was asked to consider the presidential potential of Republican Chris Christie.
"I like Chris Christie," she said of the New Jersey Governor. "I hope he runs. I just worry about this man dying in office."
Christie possesses a physique you might kindly describe as "jolly". You might also, less kindly but more realistically, compare his silhouette with that of Violet Beauregarde in Roald Dahl's Charlie and the Chocolate Factory. Violet eats a forbidden treat and is subjected to a rapid and violent expansion.
A Swiss Ball on steroids, Christie's silhouette cuts a near perfect orb but for the quiver of his mighty jowls.
These observations, I should add, amount to Christie's own, frank, admissions. Controlling his weight is an ongoing issue. But his own admissions are usually more tactfully crafted than to publicly question his chances of carking it on the job. There's more to health than just his fat, Christie retorted this week. He appeared on late night TV smashing a doughnut. Unless the doctor gives him a physical or examines his family history, Christie says Mariano should "shut up".
But surely the doctor has a point.
It's true Obama continues to struggle with cigarettes, and that his nicotine addiction could one day spell his end. But one need only look at Christie to know he probably risks a much more sudden departure.
If tax returns, birth certificates and religious leanings are considered fair fodder for Presidential nominees, I don't think it entirely unreasonable for a pulse to be a prerequisite, too. Being obese might not stop a person doing the job, but being dead would be a hindrance.