Surrounded by US. Secret Service agents, Donald Trump, president and chief executive of Trump Organization Inc. and 2016 Republican presidential candidate, center, waves to attendees as he leaves a campaign rally in Muscatine, Iowa, U.S., on Sunday, Jan. 24, 2016. The collapsing center of U.S. politics poses a growing threat to global business, according to Davos delegates who say they're watching anxiously as Trump and Bernie Sanders ride a populist wave in the presidential election. Photographer: Daniel Acker/Bloomberg via Getty Images
