He seems to have inspired "Chuck Norris" stories avant-la-lettre: in one, he was walking up to give a speech when he was shot by a would-be assassin. The bullet penetrated the bible he had in his front pocket and lodged into his chest. He stood up, gave a two hour speech, and then went to the hospital. Some versions of the story have him starting the speech holding up the bloody bible and announcing, "You see, it takes more than one bullet to kill a Bull Moose!"
John F. Kennedy was sick throughout high school, with a "blood illness." He was originally enrolled at Princeton and had to drop out due to his sickness; his father took him to Europe for a year to heal and then wrote the Harvard admissions to get him enrolled there. Young pictures of him look sickly.