CANDIDATES, ENTER THIS DEBATE ON THE HEELS OF SOME PRETTY BIG ENDORSEMENTS FOR KAMALA HARRIS, MEMBERS OF THE CHENEY FAMILY, LONGTIME AND STAUNCH REPUBLICANS FOR DONALD TRUMP, THE NATIONAL FRATERNAL ORDER OF POLICE, IT'S ONE OF THE MOST ANTICIPATED PRESIDENTIAL DEBATES IN U.S. HISTORY. VICE PRESIDENT HARRIS TOUCHING DOWN IN PHILADELPHIA, PENNSYLVANIA, JUST BEFORE 6 P.M. EASTERN TODAY. FORMER PRESIDENT DONALD TRUMP IS SET TO ARRIVE IN THE CITY OF BROTHERLY LOVE AROUND THE SAME TIME TOMORROW. SECURITY WILL BE TIGHT AT THE NATIONAL CONSTITUTION CENTER. INSIDE, A SIMPLE SETUP, A 90 MINUTE DEBATE MODERATED BY ABC'S DAVID MUIR AND LINSEY DAVIS. THE CANDIDATES WILL STAND BEHIND LECTERNS. THERE WILL BE NO OPENING STATEMENTS, NO LIVE AUDIENCE AND NO PRE-WRITTEN NOTES. JUST A PEN, PAPER AND BOTTLE OF WATER FOR EACH CANDIDATE. MIKE PHONES WILL BE MUTED WHEN THE OTHER CANDIDATE IS SPEAKING, BOTH PREPARING FOR THIS CONSEQUENTIAL APPEARANCE BEFORE THE AMERICAN PEOPLE. SO HE'S BEEN AT THIS BEFORE FOR, UH, HE HAS A SENSE FOR IT, BUT MOST OF IT IS INSTINCT, NOT PRACTICE. DONALD TRUMP ENTERS HIS SEVENTH GENERAL ELECTION DEBATE, WHICH IS A RECORD HARRIS PREPPING OVER THE WEEKEND IN PITTSBURGH, WHICH IS ACTUALLY BEING PREPARED AND BEING GIVEN THE HELP OF SOME OF THE ADVISERS WHO HELPED HILLARY CLINTON PREP FOR HER 2016 DEBATE WITH DONALD TRUMP. THE DEBATE COMES AT A PIVOTAL TIME. ELECTION DAY IS JUST WEEKS AWAY, AND SOME STATES BEGIN EARLY VOTING IN JUST DAYS. EXPERTS SAY MANY HAVE MADE UP THEIR MINDS, BUT THE CANDIDATES WILL STILL WORK TO SWAY UNDECIDED VOTERS. >> THOSE UNDECIDEDS, IT MIGHT. IT'S A MARGINAL GROUP. IT'S A IT'S A SMALL GROUP. UH, BUT, YOU KNOW, THIS ELECTION IS GOING TO BE A MARGINAL ELECTION. IT'S GOING TO BE DECIDED BY A SMALL AMOUNT OF VOTES. >> A NEW PEW RESEARCH POLL OUT TODAY INDICATES THIS IS A HEAD TO HEAD MATCHUP WITH BOTH CANDIDATES RECEIVING 49% SUPPORT AMONG REGISTERED VOTERS HERE IN PHILADELPHIA, LELAND