Is Barack Obama's duty to hear the voices of the entire country, or is it to heed the entreaties of his allies on the left and in the Democratic Party?That is one of the simplest, and also one of the most complex, questions of our time. To ask it is to please conservatives who argue that Obama consistently ignores their impulses and ideas. To answer it pleases liberals who want to believe that their impulses and ideas are squarely in the national interest.Here's the ideal: As a nation, the American people select only two officeholders, the president and the vice president.