The populists' popularity has eroded since 16 people were killed two years ago when a concrete canopy collapsed at a train station in Serbia's north, setting off a wave of youth protests that demanded accountability for the disaster and justice for the victims.
Vilified by pro-government media, students have cycled and walked through the country to reach voters in rural areas, which serve as traditional strongholds for President Vucic. Admirers view him as a capable leader who can steer the nation through global uncertainties, an image carefully crafted by the mainstream media.
A students' victory likely would resonate beyond Serbia as countries across Europe face youth and student protests. Meanwhile, authorities have warned that any protests that might erupt to claim fraud in case of his party's triumph would be immediately quashed.
Both international and local election monitors have already expressed concern about the safety and fairness of an election campaign marked by detentions, near-total government control over the media and reports of surveillance and cyberattacks against activists.
Serbia is holding a parliamentary election on Sunday that represents the most uncertain vote in recent years, with the main contenders polling neck-and-neck.
The state election commission is not expected to release the official tally before Monday.