Retired neurosurgeon Dr. Ben Carson, 2016 Republican candidate, surrounded by Secret Service agents, greets supporters at the conclusion of a town hall event at the Northside Cafe, January 5, 2016, in Winterset, Iowa. Carson is running against a large field of GOP candidates, including real estate mogul Donald J. Trump, Texas Sen. Ted Cruz and Florida Sen. Marco Rubio ahead of Iowa's first-in-the-nation caucuses February 1. Photo by Mike Theiler/UPI