Posters for U.S. Republican presidential candidate Rick Santorum are seen at his campaign headquarters in Urbandale, Iowa, the United States, Dec. 31, 2011. As the first contest for U.S. Republican Party to nominate their presidential candidate draws near, GOP hopefuls and their army of volunteers began their final dash Saturday towards the caucuses next week in Iowa, foregoing the New Year's Holidays. [Xinhua/Zhang Jun]