“„If supporters of federal curbs on political campaign spending by corporations were hoping that Chief Justice John G. Roberts, Jr., and Justice Samuel A. Alito, Jr., would be hesitant to strike down such restrictions, they could take no comfort from the Supreme Court’s 93-minute hearing Wednesday on that historic question. Despite the best efforts of four other Justices to argue for restraint, the strongest impression was that they had not convinced the two members of the Court thought to be still open to an exercise in modesty. At least the immediate prospect was for a sweeping declaration of independence in politics for companies and advocacy groups formed as corporations.