President Trump’s relationship to risk has often come down to an abiding self-belief: It will all probably work out for him because it generally has.

“Whatever happens, happens,” he said in 1991, declaring himself a “great fatalist” as his business fortunes wobbled.

“We’ll see what happens,” he said of North Korean nuclear diplomacy two years ago, blithely predicting that all would be fine.

“Risk plays a part in everything we do,” he advised in one of his pre-presidential how-to books. “I could get hit by a bus while I am crossing the street. Things happen.”

Yet the things that have happened this time — a president who has consistently played down the dangers of a deadly virus, joining the ranks of hospitalized patients in his high-risk demographic — are nothing like the circumstances of Mr. Trump’s past feats of political, financial and reputational survival.

He is, instead, facing something almost entirely unfamiliar to him: genuine uncertainty and peril, a moment when the comforts of his office and surname can only take him so far.

If anything, the toll of the virus, on Mr. Trump and his nation, has reinforced how little his life of chance-taking had prepared him for the cold math of infectious disease.

In business, he has transcended consistent misfires with the risk-cushioning assistance of tax-avoidance schemes, bankruptcy court, his father’s riches and a manicured vision of televised success on “The Apprentice.”

In politics, he has survived gambits that might have ended any modern presidency before his — urging a foreign government to investigate a rival, questioning the valor of war heroes, equivocating on white supremacy — because Republican allies have wagered that he is worth the trouble.

But the pandemic could be neither browbeaten nor charmed. It is not impressed with his Nielsen ratings. It is not