James K. Polk, the eleventh president of the United States, provides an object lesson in political effectiveness. The day he entered the White House, Polk remarked that he had four major policy goals for his administration, all of which he accomplished in the course of his one-term presidency. His leadership was enhanced by the clarity of his aims, the tenacity with which he advanced them, and his capacity to identify and employ hitherto unrecognized sources of power. Polk was more effective at bringing his policies into existence than at anticipating their consequences, however. He presided over a 1.2 million-square-mile increase in the nation, but he did not foresee the likelihood that there would be contention between the free and slave states over the status of slavery in the new territory. Not only did such contention occur, it spiraled in the years after Polk left office and came to head with the Civil War.