Law professor and political outsider Kais Saied was leading Tunisia's presidential polls with just over half of the votes counted, the electoral commission said Monday, in the country's second free vote for head of state since the 2011 Arab Spring.
Saied was on 18.7 percent, leading imprisoned media magnate Nabil Karoui, who was on 15.5 percent, according to the electoral commission, ISIE.
Prime Minister Youssef Chahed, a presidential hopeful whose popularity has been tarnished by a sluggish economy and the rising cost of living, could well turn out to be the election's biggest loser.
ISIE figures showed him in fifth place with 7.4 percent of the vote, trailing both Islamist-inspired Ennahdha party candidate Abdelfattah Mourou and former defence minister Abdelkarim Zbidi.
"The anti-system strategy has won," ISIE member Adil Brinsi told AFP, but added: "It's not finished yet. Mourou could very easily move from third to second place, in front of Karoui."
Local papers splashed photos across their front pages of Saied and Karoui after exit polls showed they had likely qualified for the second round of voting.
"Political earthquake," read the headline of Arabic language Echourouk newspaper, while Francophone Le Temps entitled its editorial "The Slap".
The result was a major upset for Tunisia's political establishment, in place since the uprising eight years ago that ousted dictator Zine El Abidine Ben Ali.
It could usher in a period of uncertainty for the fledgling north African democracy, the sole success story of the Arab Spring revolts.
ISIE reported low turnout at 45 percent, down from 64 percent in the country's first democratic polls in 2014.
"The abstention was a sign of a rejection of the system rather than disinterest," said political scientist Hamza Meddeb.
"People are fed up with a political class which failed to respond to their economic and social expectations."
Late Sunday, Chahed urged liberals and centrists to unite for legislative elections set for October 6, saying low participation was "bad for the democratic transition".
'Wait and see'
The election comes against a backdrop of serious social and economic challenges.
Karoui, a 56-year-old media magnate, has been behind bars since August 23 on charges of money laundering.
Tunisia's judiciary has refused to release him three times, but his lawyers said Monday they would make a fourth request within 24 hours.
"Nabil Karoui is combative, optimistic, and he is only asking for one thing: to finally be free to exercise his rights," said lawyer Mohamed Zaanouni.
A controversial businessman, labelled a "populist" by critics, Karoui built his appeal by using his Nessma television channel to launch charity campaigns, handing out food aid to some of the country's poorest.
Brinsi said the magnate would be allowed to run as long as "the judicial system does not announce a ruling on Karoui's case".
A conviction before the run-off vote would mean Saied could face the third-placed candidate, he said.
Political neophyte Saied is a highly conservative constitutionalist who has shunned political parties and mass rallies; instead, he has opted to go door-to-door to explain his policies.
A social conservative, he has defended the death penalty, criminalisation of homosexuality and a sexual assault law that punishes unmarried couples who engage in public displays of affection.
He also advocates a rigorous overhaul of the constitution and voting system, to decentralise power "so that the will of the people penetrates into central government and puts an end to corruption".
"It's going to be new," said a baker named Said on Monday, issuing a wry smile.
"We'll have to wait and see. Anyway, what matters in Tunisia is the parliament."
Legislative polls are set for October 6.
'Disgust' with political elite
Sunday's vote was marked by apathy among young voters in particular, pushing ISIE's head to put out an emergency call to them Sunday an hour before polls closed.
On Sunday morning, senior citizen Adil Toumi had asked as he voted in the capital: "Where are the young people?"
Hamza Meddeb told AFP that "disgust with the political elite seems to have resulted in a vote for outsiders."
Distrust of the political establishment runs high in Tunisia, where unemployment is at 15 percent and the cost of living has risen by close to a third since 2016.
Jihadist attacks have exacted a heavy toll on the key tourism sector.
Around 70,000 security forces were mobilised for the polls.
The date of a second and final round between the top two candidates has not been announced, but it must be held by October 23 at the latest and may even take place on the same day as legislative polls.