NEW YORK, NY - SEPTEMBER 03: GOP presidential front-runner Donald Trump holds up a pledge at a news conference in Manhattan after he signed the pledge Thursday to support the Republican nominee in the 2016 general election, ruling out a third-party or independent run on September 3, 2015 in New York City. Trump made the announcement following a meeting with Republican National Committee chairman Reince Priebus. Trump stressed repeatedly in the news conference that he is leading in all national polls. (Photo by Spencer Platt/Getty Images)
