Forty years ago this month, Paris exploded in left-wing student riots that led to a nationwide general strike. The revolutionary fervor of France's soixante-huitards ('68ers) spread widely, including to American campuses. If you're wondering when the Good '60s of peace, love and civil rights gave way to the Bad '60s of anarchy and violence, May 1968 is as good a historical pivot point as any.John McCain was in the Hanoi Hilton at the time. Barack Obama was 6 years old. Yet the restless spirit of '68 haunts this year's presidential campaign, especially the White House bid of Mr. Obama, who,...