Anti-establishment candidate Virginia Raggi has been elected the first female Mayor of Rome in a blow for the city's bid for the 2024 Summer Olympic and Paralympic Games.
Raggi, who represents the Five Star Movement, won the two-horse runoff after Democrat opponent Roberto Giachetti conceded defeat an hour after polls closed.
She had led voting by a two-to-one margin with more than 80 per cent of ballots counted.
Her support came largely as a result of public anger over political corruption and deteriorating city services.
"I will work to bring legality and transparency," she claimed, adding: "with us a new era begins".
The 37-year-old has repeatedly outlined her opposition to the Olympic and Paralympic bid, and, at the very least now appears likely to push for a referendum.
Raggi had been opposed by Italian Prime Minister Matteo Renzi, a strong supporter of Rome 2024, but his authority suffered a further blow when Chiara Appendino, another candidate from the Five Star Movement started by comedian Beppe Grillo, enjoyed a surprise Mayoral victory in Turin.
Renzi has admitted that he can do little to stop the Olympic bid being abandoned if a new Rome Mayor pushes for such a decision.
The Bid Committee will now be pinning their hopes on Raggi becoming more sympathetic now campaigning is over.
Director general Diana Bianchedi here told insidethegames earlier this month that there is “no possibility” Rome 2024 will withdraw if Raggi is successful.
Raggi has said the bid would encourage corruption to re-emerge and that they should focus on solving political and economic problems.
But she gave Olympic supporters a ray of hope earlier this week when she claimed the Games could “definitely be a chance of development and growth".
She claimed the city's problems should be solved first but said that a referendum would be held if citizens asked ''through a petition''.
The Rome Municipality's Capital Committee on Referendums ruled in April that a public vote on whether to press ahead with the bid could be held following its submission by the Italian Radicals Political Party, so long as there were 30,000 signatures calling for one.
However, the City Council backtracked on this decision after receiving a letter from the Italian National Olympic Committee (CONI) which urged them to reconsider, prompting supporters of a referendum to claim the decision had been “seriously illegitimate”.
Rome are bidding for the Olympics and Paralympics in eight years' time along with Budapest, Los Angeles and Paris.
The International Olympic Committee is due to elect its chosen host at its Session in Lima in September 2017.