In 1912, John Shrenk tried to kill former President Theodore Roosevelt on a street in Milwaukee, Wisconsin. Only a few yards from where the politician was walking, Shrenk fired a pistol straight at Roosevelt's heart. The bullet hit Roosevelt, who was making a comeback bid for the White House. But in one of the most extraordinary twists in the history of assassination, Roosevelt staggered to his feet, boasted to the crowd that he was all right, and went on to deliver a 50-minute speech with a bullet lodged in his chest.

Ironically, one decade earlier a successful assassination had made Roosevelt president. The death of President William McKinley on September 14, 1901, by an assassin's bullet had made Roosevelt, at age 42, the youngest president in history. The Republican served two terms marked by personal outspokenness and strong exercise of executive branch powers. Although his final years in office were tumultuous, he...