Barack Obama once came close to injecting heroin, but balked when a junkie pulled out the needle and rubber tubing. Obama and Mitt Romney are descended from polygamous great-grandfathers who had five wives apiece. Rudy Giuliani's first wife was his second cousin. Liberal Democrat Hillary Rodham Clinton was once a conservative Republican "Goldwater Girl." Such are the plot twists in the remarkable saga of the 2008 presidential campaign,...