In October, Sarah Palin announced that she would not run for president in 2012, ending the media frenzy around her potential candidacy even as she vowed to remain politically active and influential. “I will continue driving the discussion for freedom and free markets,” she wrote in an e-mail to her supporters. Just over three months later, her attempts to wield influence in the presidential campaign the way she did during the 2010 midterm elections have largely fizzled. And the Tea Party movement that she helped to turn into a powerful political force in 2010 has so far displayed little impact...