COME JANUARY, a new president will take charge of a nation diminished, an America that is far shakier economically, less secure militarily, and less respected internationally than it was eight years before. The nation needs a chief executive who has the temperament and the nerves to shepherd Americans through what promises to be a grueling period — and who has the vision to restore this country to its place of leadership in the world. Such a leader is at hand. With great enthusiasm, the Globe endorses Senator Barack Obama for president. The charismatic Democrat from Illinois has the ability to...