No winner of a hard-fought, down-to-the-wire presidential nomination battle ever received a stronger boost from his vanquished foe than Senator Barack Obama picked up from Senator Hillary Rodham Clinton here Tuesday. After days of backstage carping among both her supporters and his, no one knew exactly what to expect. Obama didn’t just beat a strong and popular candidate; he snatched the reins from the party’s old guard and ticked off a former President, Bill Clinton, in the process
