President Trump will tweet Friday morning that he is nominating State Department Spokeswoman Heather Nauert to be the U.S. Ambassador to the United Nations, replacing outgoing official Nikki Haley, multiple sources tell Fox News. Back in October, Nauert, a former Fox News host, was believed to be a "leading contender" for the position, sources familiar with the selection process said at the time. Haley unexpectedly announced her resignation in October and promised to serve in her role through the end of 2018. At the time, she described her time in the position as a "blessing," but offered no reason for...