It had been expected that Janković would seek a return to City Hall in the 25 March by-election, as he had entered the December general election with the goal of becoming prime minister but failed to form a government despite emerging as the winner.

Janković recalled how he had said prior to the general election that he saw himself in the executive branch, not as an MP. The decision, therefore, was "either the government or the mayorship".

However, he hinted that he still saw himself as a potential prime minister. "In the event of another early election, the people would not back parties that change their mind every hour and every day," he said, confident that his Positive Slovenia would win by a bigger margin and put together a government.

Janković won the last mayoral election in 2010 in a landslide, picking up nearly two-thirds of the vote and securing an absolute majority in city council for his Zoran Janković List.

However, the New Slovenia (NSi) and the Democrats (SDS), which had fielded separate candidates two years ago, have now joined forces and backed Mojca Kucler Dolinar, a former higher education minister.

Other candidates include Matjaž Glavan of the People's Party (SLS), former MP Vito Rožej (Zares) and Miha Jazbinšek, a city councillor for the Greens.