The White House has a long, storied tradition of hiding the medical issues of the president from the American public. Ronald Reagan’s administration hid signs of his dementia; FDR hid his paralysis for years; Woodrow Wilson spent his last year and a half as president debilitated by a stroke that left him blind in one eye while his wife worked as a “shadow president.”

On Ian Explains, Ian Bremmer explains why allies worry about the growing concerns around President Biden’s health, fitness for office, and stamina to lead the country for another four years. While there’s no evidence Biden is suffering from a distinct illness like Wilson or FDR, his disastrous debate performance last month made many question his ability to lead the country and the world for a second term.