Serbia's long-serving leader, Aleksandar Vučić, conceded defeat on Sunday, opening the door to a seismic political shift after a historic election. Tens of thousands of people flooded the streets of Serbia’s capital on Sunday night, bringing traffic to a halt and celebrating after long-time leader Aleksandar Vucic conceded defeat in. Aleksandar Vucic conceded defeat to Serbia's student-backed movement after nearly two years of anti-corruption protests.