Harry B. Partridge points out that most presidents whose names have contained a penultimate L — Ronald Reagan, Abraham Lincoln, James Garfield, Franklin Roosevelt, John Fitzgerald Kennedy — have died in office or survived an assassination attempt. He speculates that Gerald Ford survived because he was born Leslie Lynch King Jr., and that Theodore Roosevelt was divinely spared because THEO means God. (James Polk died three months after leaving office.)
Partridge also notes that a name with patronymic prefix (Mc, Fitz, etc.) is invariably fatal. To date there have been only two: William McKinley and John Fitzgerald Kennedy.
See Tecumseh’s Curse.