GOP hopefuls debate in Iowa sans Trump (23 images)

2016 Republican presidential candidates (L-R) New Jersey Gov. Chris Christie, retired neurosurgeon Ben Carson, former Florida Gov. Jeb Bush and Florida Sen. Marco Rubio share a laugh at the conclusion of a GOP debate hosted by Fox News, January 28, 2016, in Des Moines, Iowa. Photo by Mike Theiler/UPI

2016 Republican presidential candidates (L-R) Kentucky Sen. Rand Paul , New Jersey Gov. Chris Christie, retired neurosurgeon Ben Carson, Texas Sen. Ted Cruz , Florida Sen. Marco Rubio, Former Florida Gov. Jeb Bush and Ohio Gov. John Kasich gather on stage prior to 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

2016 Republican presidential candidate Florida Sen. Marco Rubio responds to a question during a GOP debate hosted by Fox News, January 28, 2016, in Des Moines, Iowa. Photo by Mike Theiler/UPI

2016 Republican presidential candidate former Florida Gov. Jeb Bush listens to remarks during a GOP debate hosted by Fox News, January 28, 2016, in Des Moines, Iowa. Photo by Mike Theiler/UPI