WASHINGTON — To some Republicans, the start of this presidential term is their moment, their chance to become the permanent majority party with a new vision that goes by various names: the ownership society, the Conservative New Deal, the New New Deal. But can they really significantly trim seven decades of ever-growing programs? Can the New Deal government be rolled back? Even some devout conservatives doubt that this can happen, and not only because of Democratic opposition. The skeptics believe that most Americans are unwilling to change the only kind of government that most of them have ever known. After...