As a barometer of his popularity, Barack Obama could do worse than refer to his book sales. The senator's The Audacity of Hope, currently ranked 5th among books on Amazon and set to be no. 1 on the Times non-fiction list Sunday, has become nothing short of a best-seller. In less than a month, it has sold 182,000 copies and is in its seventh printing. By way of comparison, Trent Lott's latest has moved a mere 11,000 units since its publication in August 2005; Jesse Helms has fared even worse at 3,000.