0258 GMT November 20, 2019
Saied was on 19 percent, leading imprisoned media magnate Nabil Karoui, who was on 14.9 percent, and ahead of the candidate from the Ennahdha party Abdelfattah Mourou (13.1 percent), according to the electoral organ Independent High Authority for Elections (ISIE), AFP reported.
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 on 7.4 percent of votes, behind Defense Minister Abdelkarim Zbidi, who was on 9.6 percent.
"The anti-system strategy has won," ISIE member Adil Brinsi told AFP, warning however there was still a lot to play for among the three leading players.
"It's not finished yet. Mourou could very easily move from third to second place, in front of Karoui," he added.
Local papers splashed photos across their front pages of law professor Saied and magnate Karoui, after exit polls showed they had qualified for the second round of voting.
"An unexpected verdict," ran a headline in La Presse.
Le Temps titled its editorial "The Slap", while the Arabic language Echourouk newspaper highlighted a "political earthquake" and a "tsunami" in the Maghreb.
It all points towards a major upset for Tunisia's political establishment, in place since the 2011 uprising that ousted former leader Zine El Abidine Ben Ali.
Tunisia's electoral commission reported low turnout at 45 percent, down from 64 percent in the country's first democratic polls in 2014.
Late Sunday, Chahed called on the liberal and centrist camps to band together for legislative elections set for October 6, voicing concern that 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 and Tunisia's Judiciary has refused to release him three times.
"So long as the judicial system does not announce a ruling on Karoui's case, nothing will change in the second round with regard to this candidate," in the event that he makes it to the runoff, Brinsi said.
However, "if he is convicted between the first and second round, it would be necessary to bypass him and organize a second round involving the third-placed candidate".
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.
His apparent rival is political neophyte Saied.
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.
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, October 6.