American presidential campaigns are traditionally so gruelling that the winner, almost by definition, is healthy enough for the physical rigours of governing. as such, there are limited examples of serious illness befalling the commander-in-chief. there will now be one more data point to add to the set. us president donald trump announced early on friday that he had tested positive for coronavirus.

In the few previous incidents of a surprise ailment, only a couple sent the s&p 500 sharply downwards. and three months later, the stock market was generally at higher levels, underlining the resilience and stability of the american system.

This time may be different, however. mr trump has been infected by the pathogen behind a pandemic he has consciously downplayed, all the while in the middle of a hotly contested election that will also determine control of the us congress. still, on friday morning major us stock indices were off just 1 per cent.

When president eisenhower had a heart attack in september 1955, the s&p 500 fell nearly 7 per cent. on the news of the kennedy assassination in 1963, shares dropped 3 per cent. the most recent health scares occurred during the tenure of ronald reagan. he survived an assassination attempt and numerous surgeries. three major operations barely moved the markets on the given day.

Among 10 presidential health incidents between 1923 (death of president harding) and 1987 (reagans surgery), in only one instance was the stock market down more than 1 per cent three months later. that was president trumans hospitalisation in 1952.

In addition to fit presidents, the us has generally been able to rely on the resilience of a broader set of institutions. many believe that robustness is also a ballot proposition in this election. amid a pandemic where monetary stimulus is unprecedented and asset prices continue to soar, the forces that drive financial markets are equally worthy of debate. particularly when they shrug off the health issues of the most powerful person in the world.

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