No president in the modern age has had to face an “insurgency” of relentless criticism from not one, but two former presidents—both dedicated to undermining his policies. Bill Clinton’s appearance on Fox News yesterday is a case in point, calculated to score points through attacks on the “right-wing conspiracy” and President Bush. Jimmy Carter is still trying to build his legacy and sell books—but he’s not much more than a gadfly these days. William Jefferson Clinton is important for a number of reasons: He’s still the heart and soul of the Democratic Party; European liberals love him; and his wife...