* Sisi shot to popularity after ousting Mursi
* Served as Mubarak's military intelligence chief
* Rights activists fear return to authoritarian rule
* Egyptians may turn against him if problems persist
By Michael Georgy
CAIRO, March 26 (Reuters) - Abdel Fattah al-Sisi, who announced on Wednesday he would run for president in a vote he is expected to win easily, has gained cult-like adulation since he toppled Egypt's first freely elected leader in July.
Supporters see Sisi as a saviour who can end the political turmoil dogging Egypt since a popular uprising ended Hosni Mubarak's three decades of one-man rule in 2011.
If he becomes president he will become the latest in a line of Egyptian rulers drawn from the military that was only briefly broken during Islamist President Mohamed Mursi's year in office.
Sisi resigned from his posts of army chief and defence minister on Wednesday so that he could run for president.
Critics fear Sisi will become yet another authoritarian leader who will preserve the interests of the military and the Mubarak-era establishment, crushing the hopes of democracy, reform and social justice aroused by the youthful protests that swept away Mubarak - but not the system that had sustained him.
The Muslim Brotherhood, which had propelled Mursi to power at the ballot box, accuses the army of staging a coup against a legitimately chosen president and destroying democracy.
Sisi has generated sky-high expectations, but has outlined no detailed solutions for the poverty, energy shortages and unemployment that afflict many of Egypt's 85 million people.
Nor has he quelled an Islamist insurgency based in the Sinai peninsula that has intensified since Mursi's overthrow.
That sets up the 59-year-old for a possible fall from grace in a nation where street protests on a scale never seen in Mubarak's day have helped oust two presidents in three years.
In a pre-recorded speech to the nation announcing he would contest the election, Sisi said he would take on challenges but warned Egyptians he could not perform miracles.
The world knew little of Sisi before he appeared on television on July 3 to announce the removal of Mursi after vast crowds demanded he resign, and to promise new elections.
Sisi had kept a low profile as Mubarak's head of military intelligence. It was Mursi who appointed him army chief and defence minister in August 2012, in a mistaken calculation that the military would let the Brotherhood pursue its Islamist agenda as long as its own entrenched privileges were kept safe.
Mursi may have been swayed by Sisi's reputation as a pious Muslim. Some Brotherhood leaders have said he used to join them for prayers and wept while reciting verses from the Koran.
But Mursi appeared deaf to discontent on the streets which rose to a crescendo after he grabbed sweeping powers to ram through an Islamist-tinted constitution. The Brotherhood's perceived mismanagement of the economy only fuelled unrest.
When a carefully orchestrated anti-Mursi campaign gathered steam, Sisi picked his moment and gave the man who appointed him a 48-hour ultimatum to resign or face military action.
He then deposed a defiant Mursi and carted him off to jail, eventually to face charges that could carry the death penalty.
Egyptians weary of endless upheaval hailed Sisi, even when the new army-backed government began a fierce campaign to crush the Brotherhood, which as the country's best-organised political force, had won every national vote held after Mubarak's fall.
Security forces killed hundreds of Mursi supporters in the streets in August in the bloodiest civil unrest in Egypt's modern history. They jailed the leaders of the Brotherhood, which the government then denounced as a terrorist organisation, despite its renunciation of violence decades earlier.
But the Sisi bandwagon has rolled on, with images of him in sunglasses and beret adorning posters, t-shirts, chocolates and even women's underwear in this conservative, mainly Muslim land.
Sisi has never publicly resisted the relentless praise.
In an unpublished segment of an interview with al Masry al-Youm daily that was leaked in an audio online, he spoke of a vision that suggested he was destined to be a great leader.
"In a dream I had 35 years ago, I was raising a sword with the phrase 'There is no God but God' written on it in red," said Sisi, who rose from a childhood in the dirt lanes of Cairo's Gamaliya district to the highest rank in the biggest Arab army.
PERILS OF POWER
Born on Nov. 19, 1954, he was the youngest member of the military council that ruled for 18 turbulent months after Mubarak resigned on Feb. 11, 2011.
Western diplomats say Sisi only recently took what they described as the risky decision to run for office. "The army may act if things go wrong and its image is tarnished. His fall could be sudden and sharp," said a senior European diplomat.
A few months before he unseated Mursi in 2013, Sisi had suggested he would never stage a military takeover, let alone run for president, despite his suspicions of the Brotherhood.
"With all respect for those who say to the army: 'go into the street', if this happened, we wouldn't be able to speak of Egypt moving forward for 30 or 40 years," Sisi had said.
Cracks have appeared in his support base. Secular activists who backed the army takeover have joined Islamists in criticising what appears to be a systematic stifling of dissent.
Under Sisi, protesting without permission has become a crime which can be punished by a life sentence. Sisi's election would signal a return to the oppression of the past, opponents say.
"There are real fears and there are reasons for them," said lawyer and human rights activist Gamal Eid. "The current human rights abuses raise a lot of worries over Sisi ruling."
Yet amid widespread disillusion with politicians and protesters, Sisi enjoys the backing of the powerful armed forces and the Interior Ministry, as well as that of many politicians and former Mubarak officials now making a comeback.
Some of Sisi's admirers liken him to former President Gamal Abdul Nasser, a nationalist hero despite leading Egypt to catastrophic defeat against Israel in the 1967 war.
In his early childhood, Sisi showed signs of unusual discipline, people in his old neighbourhood say. While other boys played football or smoked, Sisi and his friends lifted bar-bells made of metal pipes and rocks.
"Abdel Fattah always seemed to have a goal. He had willpower," said Aatif al-Zaabalawi, a dye factory worker who used to see Sisi in Gamaliya.
Neighbours say he came from a tightly-knit religious family. A cousin, Fathi al-Sisi, who runs a handicraft shop, said the future field marshal had memorised the Koran.
Sisi's father encouraged him to work in his shop every day after school. He lived in a small apartment on the rooftop of a run-down building owned by his extended family.
Aware of the scale of Egypt's problems, Sisi may ask his compatriots for patience, said retired general Sameh Seif Elyazal, who has met the presidential favourite several times.
"He hasn't got an immediate solution for everything," Elyazal said. "I think he will tell the people ... you have to bear with me. We will suffer a little bit." (Additional reporting by Yasmine Saleh and Sameh ElBardissi; Editing by Alistair Lyon)