BUCHAREST, May 18, 2025 (BSS/AFP) - Like his far-right rival, pro-EU Bucharest mayor Nicusor Dan is campaigning on a slogan of change in Romania's presidential race.

The former math prodigy is hoping a higher turnout Sunday's second round will boost his chances against George Simion, who comfortably topped the May 4 first round of voting in the EU and NATO member bordering war-torn Ukraine.

Dan, 55, says he wants to "rebuild" the eastern European country. One of the EU's poorest members with a wide wealth disparity, it has been ruled by the same class of politicians since the end of Communism in 1989.

"It is about unity, about rebuilding, about hope... It cannot go on like this, we want change," he told thousands of cheering supporters last weekend in an emotional speech.

He has repeatedly encouraged people to vote, after turnout reached just 53 percent in the first round poll for the top post, which holds significant sway in foreign policy.

In his presidential campaign, Dan has voiced support for Ukraine and vowed to keep Romania on its "pro-Western" path, urging voters to reject Simion's "isolationist" approach.

- 'Shock' vote annulment -

Dan has said his decision to run in the race followed the shock annulment of last year's elections.

Romania's constitutional court scrapped the vote after allegations of Russian interference -- which Moscow has denied -- and a massive social media promotion in favour of the far-right frontrunner, since barred.

The political turmoil has deepened divisions in the country, which Dan hopes to heal.

Born and raised in Brasov county in Transylvania in central Romania, as a teenager he won several international math competitions and went on to study math at the University of Bucharest.

He then moved to France to continue his studies and got his PhD in Paris, before returning to Romania to help bring change and fight endemic graft.

With the country ranked as one of the EU's most corrupt by Transparency International, he became an activist battling illegal urban development.

He then turned to politics, a career his daughter has said leaves him little time "to go out" with her, though she supports him, the father-of-two told AFP.

Running for Bucharest mayor several times, Dan was eventually elected in 2020 and then re-elected for a second term in 2024.

He ran as an independent after leaving the party he founded, the Save Romania Union (USR), arguing the party should stay focused on the fight against corruption instead of civil liberties, including LGBTQ rights.

Since first being elected mayor, Dan has prided himself on having modernised the capital's heating system and its sports facilities, while succeeding in pulling the city out of bankruptcy.

- Reserved nature -

Dan is known for carefully weighing his words and for his reserved nature. He has been criticised for lacking decisiveness and for poor communication skills.

But in the fight against Simion, a football hooligan in his youth known for his sometimes violent outbursts, Dan's reserved nature may have become an asset, according to analysts.

"He is more the managerial, administrative type but he is a very decent, honest guy," political analyst Sorin Cucerai told AFP.