A former adviser to three Republican presidents called the speech Donald Trump gave before a crowd of supporters Saturday in Pennsylvania the “most divisive” he has ever heard from a president. David Gergen, a CNN political analyst who advised Presidents Richard Nixon, Gerald Ford and Ronald Reagan — and President Bill Clinton — said he found the speech “deeply disturbing” with little change from Trump’s bombastic, divisive campaign messages. Trump slammed the press — again — as “fake news,” vowed to topple Obamacare and promised to build the border wall between Mexico and the U.S.