ISTANBUL — Turkish President Recep Tayyip Erdogan on Monday confronted the tough task of uniting his deeply divided country after winning a historic run-off election to extend his two-decade rule to 2028. Turkey's longest-serving leader brushed aside a powerful opposition coalition, a biting economic crisis and widespread anger following a devastating February earthquake to beat secular challenger Kemal Kilicdaroglu in Sunday's vote. But the four-point victory margin was Erdogan’s narrowest of