IS A BIPARTISAN COALITION REQUIRED to pass legislation that would allow individuals to invest their Social Security payroll taxes in stocks and bonds? Not really. Surely, the White House will endorse a Social Security reform plan that slows the growth of benefits by roughly 40 percent, right? Don't count on it. And won't Democrats be able to attack almost any reform proposal by President Bush with political impunity? Actually, obstructing Bush carries real risks. But as for all the talk about a new paradigm, doesn't Social Security still represent the third rail of politics--touch it and you get badly hurt?...