India, Oct. 26 -- The long-serving strongman leader of Serbia, Aleksandar Vucic, conceded defeat on Sunday in an election that pitted him and his right-wing party against a diverse student-led opposition movement that spent two years protesting his Government.

It was a seismic political shift in the Balkan country where Vucic, who had been endorsed by Russian President Vladimir Putin and who denounced the student movement as a foreign-led attempt to unseat him, led with virtually absolute power for 14 years.

High turnout and gathering tensions marked the highly contested parliamentary election that was a showdown between Vucic and his right-wing Serbian Progressive Party and university students who, accusing the Government of corruption...