GOP presidential candidates attend debate in Des Moines, Iowa

2016 Republican presidential candidate retired neurosurgeon Ben Carson responds to a question as New Jersey Gov. Chris Christie listens during a GOP debate hosted by Fox News, January 28, 2016, in Des Moines, Iowa. Billionaire businessman Donald J. Trump has boycotted the debate, which is the final one before Iowa's first-in-the-nation caucuses, February 1. Photo by Mike Theiler/UPI