2016 Democratic presidential candidates Martin O'Malley, former governor of Maryland, from left, Hillary Clinton, former Secretary of State, and Senator Bernie Sanders, an independent from Vermont, participate in the Democratic presidential candidate debate in Charleston, South Carolina, U.S., on Sunday, Jan. 17, 2016. Hours before Sunday's Democratic debate, the two top Democratic contenders held a warm-up bout of sorts in multiple separate appearances on political talk shows, at a time when the polling gap between the pair has narrowed in early-voting states. Photographer: Patrick T. Fallon/Bloomberg via Getty Images
