Scholars now know that King George III, the monarch who lost America, was profoundly impaired toward the end of his reign by a disease that caused progressive insanity. Robert E. Gilbert, a political scientist at Northeastern University, argues that more than a century later America was led by a president who was also afflicted by a misunderstood and untreated mental condition that destroyed his authority and undermined his judgment. Calvin Coolidge, rated by historians as among the worst presidents in history, strode boldly into the White House in 1923 only to lose his young son 11 months later and plunge into clinical depression.

Following President Warren G. Harding’s sudden death of a heart attack, vice president Coolidge proceeded confidently to dominate the capital. He met almost daily with members of Congress, entertained them at breakfast and on the presidential yacht, corresponded extensively with influential government leaders, and upon the death of the wife of an important farm bloc leader, invited the senator to live at the White House for a while.