Republican U.S. presidential candidates (L-R) former U.S. Senator Rick Santorum, former New York Governor George Pataki, Louisiana Governor Bobby Jindal and U.S. Senator Lindsey Graham talk at the conclusion of a debate between the lowest polling candidates held before the second official Republican presidential candidates debate of the 2016 U.S. presidential campaign at the Ronald Reagan Presidential Library in Simi Valley, California, United States, September 16, 2015. REUTERS/Lucy Nicholson