U.S. Senator John McCain (L) and former Alaska governor and vice presidential candidate Sarah Palin acknowledge the crowd during a campaign rally for McCain at the Pima County Fairgrounds in Tucson, Arizona March 26, 2010. McCain, who is seeking a fifth term as U.S. Senator, received Palin's endorsement and will challenge JD Hayworth during the Republican primary in August 2010.[Reuters/Xinhua]