Like most modern presidential races, this year's campaign has given us its fair share of health lessons. First there was Bill Bradley's atrial fibrillation. Then we learned about Dick Cheney's heart attacks and bypass surgery. Now Senator John McCain is fighting a renewed battle against malignant melanoma, the deadliest and most aggressive form of skin cancer, whose incidence has grown dramatically over the past 50 years. McCain's office reported last week that doctors found two cancerous lesions--one on his left temple and the other on his left arm. An earlier melanoma was removed from his left shoulder in 1993.
As McCain...