By Nick Thorpe
BBC correspondent in Belgrade
Serbia's parliament has abolished a threshold turnout requirement - which has left the country without a head of state for more than a year, despite three successive attempts to elect one.
Nationalist Mr Nikolic is expected to run in the next election
The vote means that the country's next president will be elected by simple majority.
Analysts suggest the vote could be held in May.
On Wednesday the Serbian parliament bowed to the inevitable - and abolished the 50% turnout requirement for presidential elections in the country to be valid.
The country's last president, Milan Milutinovic, ended his term at the end of 2002 and is now one of a number of former senior officials on trial for war crimes at the Hague tribunal.
Three successive attempts to elect a successor have failed because of low turnout.
In the latest last November, Tomislav Nikolic of the ultra-nationalist Serbian Radical Party was comfortably ahead of his challengers.
Mr Nikolic is expected to stand again but it is not clear who will challenge him.
His party is already the largest in the Serbian parliament - with nearly one third of all seats - but has gone into opposition because it could not find enough allies to form a government.
Under the Serbian constitution, the speaker of parliament, Dragan Marsicanin - who is also acting president - must call elections by the first week in April.
Following a short campaign, the earliest possible date for the actual vote would be mid-May.