The pro-Western Tadic is seeking re-election in a tough campaign against nationalist Tomislav Nikolic, a populist who favors closer ties with Russia and has been connecting with working-class Serbs who have been struggling against economic headwinds.
The final pre-elections polls gave Tadic the lead despite serious unemployment in the Balkans state,
Nikolic's campaign has been a balancing act between increasing ties with the West and the more-isolationist sentiment that Nikolic has been cultivating. At stake are Serbia's ties with the European Union, The New York Times said.
Nikolic has accused Tadic of being overly anxious to forge closer ties with the Unites States and Western Europe, and of rigging the vote in last month's primary voting.