By Tarek Amara and Mohammed Argoubi
TUNIS (Reuters) - Kais Saied, a political outsider who is backed by Islamists and leftist and wants to remake national politics, won a landslide victory in Tunisia's presidential election which he hailed as a "new revolution".
Saied won 73% of the votes cast in Sunday's election, according to preliminary official results released by the electoral commission on Monday, and turnout was 55%. His opponent, Nabil Karoui, had already conceded defeat.
Saied's victory is a stinging rebuke for a governing elite that has failed to improve living standards or end corruption since the 2011 revolution in the North African country that introduced democracy and ushered in the "Arab Spring".
Saied, a 61-year-old retired law professor, wants to introduce an experimental form of direct democracy. But he has no political party of his own and faces big challenges including high inflation and unemployment.
"What I have done is a new revolution," Saied told a crowd of supporters gathered at his home in the Mnihla district on the outskirts of Tunis after his landslide victory became clear. "I tell Tunisians that you have impressed the world."
Large crowds of people waving Tunisian flags and chanting many of the old songs and slogans from the 2011 uprising filled the central Habib Bourguiba Street late on Sunday and celebrated into the early hours of Monday.
Olfa Radouan, a 53-year-old woman who brought her husband and two children to celebrate Saied's victory, said she understood that he would face big challenges.
"It will not be easy. He will face a complicated political situation, a very difficult economic situation, unstoppable social demands," she said.
Though exit polls had given Saied a huge lead soon after voting ended on Sunday, his opponent had left open the possibility that he might appeal against the result.
Nabil Karoui, a media mogul, was detained in August pending a verdict in his trial for money laundering and tax evasion - accusations which he denies - and was released only last Wednesday. But Karoui conceded defeat and congratulated him several hours before the preliminary results were announced.
Even with a large mandate, the new president has less direct control of policy than the prime minister and both will quickly face a series of tough challenges.
Tunisia has a deeply fragmented legislature in which the largest party, the moderate Islamist Ennahda, has only 52 of the 219 seats.
As the biggest party, Ennahda can name the prime minister, but he will then have only two months to form a governing coalition that can command a majority in parliament - something that may prove highly complex.
If Ennahda's choice fails to form a government, the new president can name an alternative candidate for prime minister to embark on a new round of coalition talks. If parliament still cannot agree, there would be a new election.
Though Saied has won the support of both Islamists and leftists, his radical but socially conservative politics do not neatly chime with either group. It has left both his critics and supporters struggling to define him.
He wants Tunisians to elect small local councils based on the character of their representatives rather than party or ideology. They would in turn choose regional representatives who would choose national ones.
With politicians in Tunis dominating the post-revolutionary era, a period that included many economic disappointments, that sort of radical decentralization appeals to many of those who rose up across the country eight years ago.
The government faces unemployment of about 15% nationally and 30% in some cities, inflation of 6.8%, high public debt and a weak dinar.
Foreign lenders including the International Monetary Fund have called for fiscal tightening and a reduction of the public sector wage bill.
Those policies are all deeply unpopular and the country's powerful union has proven able to mobilize large numbers of people and paralyze parts of the government with strikes.
(Reporting by Tarek Amara and Mohammed Argoubi, Writing by Angus McDowall, Editing by Timothy Heritage)