Is there a political philosophy behind the most captivating politician in America not named Barack Obama? As Sarah Palin begins a nationwide book tour, which is generating excitement and exasperation on par with her vice-presidential run last year, her ultimate goal remains a mystery. "If she grows, she'll be the Republican nominee. More than anybody else in the party, her future is in her hands," former House Speaker Newt Gingrich has said. Indeed her ability in many ways to stand at the Republican Party's center has some comparing Palin to Gingrich. Her influence was seen in New York's 23rd Congressional District two weeks ago. But, Dan Balz wrote in Sunday's Washington Post, this book tour is a test for Palin to see "whether she has the capacity to grow politically."