Staff and volunteers work for U.S. Republican presidential candidate Mitt Romney at his campaign headquarters in Des Moines, 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]