"Where Egypt goes, the region follows" is an adage often quoted by academics teaching the arcane politics of the Arab world.
Wednesday's military takeover in Cairo, toppling Islamists who had so recently swept to power in one of many Arab upheavals, looks set to have a profound impact beyond Egypt's borders.
The fall of President Mohamed Morsi and his Muslim Brotherhood, brought down by an army spurred into action by mass protests, marks a strategic reverse for political Islam in the Arab world.
Egypt is not only the most populous Arab country and a bellwether for the region. It is the birthplace of this pan-Islamist movement and a guiding light for the 2011 Arab Spring upheavals that toppled dictatorships and propelled Islamists into power.
A setback for the Brotherhood in their heartland raises questions about their ability to govern, from Tunisia to Syria. And the Brothers have been dealt a crippling blow.
Egyptians came out in even greater numbers to oppose Morsi - only a year after they elected him - than to depose Hosni Mubarak, the former air force commander brought down by the Tahrir Square revolt of 2011.
That will be a stain on the reputation of the Brothers, the standard-bearers of mainstream Sunni political Islam since they were founded in Egypt in 1928.
Outlawed for more than eight decades, the secretive Brotherhood emerged after the fall of Mubarak as Egypt's best organised party - in fact the only properly organised body apart from the armed forces.
Sixty years of military-dominated rule, beginning with Gamal Abdel Nasser, whose pan-Arab rhetoric thundered across the region and helped shape the post-colonial Arab world, left no space for conventional democratic politics.
The Brothers were able to exploit that gap.
The force behind the Arab revolutions of 2011 were mainly middle-class, disaffected young people. But it was Islamist groups, such as the Brotherhood, that were best positioned to gain from the transition.
Egypt's Brothers won a string of elections including the presidency, making Morsi the country's first democratically elected president. But, like related organisations such as the ruling Ennahda party in Tunisia, they seemed unable to shake off the secretive habits of their past.
Critics say they sought to occupy all the institutions of government and turn them into fortresses for the Brotherhood rather than servants of the nation.
Public repudiation of this approach, followed by the army's ejection of Morsi, makes their collapse look total, and a warning to Islamists across the region.
"It is a disaster. It is a hard blow to the entire Islamist movement," said Fawaz Gerges, Professor of Arab worldern Politics at the London School of Economics.
"The dismal performance by Morsi and the Muslim Brotherhood undermines the Islamist image, standing and narrative throughout the region, in Egypt, in Jordan and even in Turkey. It raises questions about their competence, their ability to manage."
While everyone acknowledges that post-Mubarak Egypt faced intractable problems - from economic collapse as the government's crony capitalists fled, to a security vacuum as police forces pulled back - almost no one imagined that a movement as well-oiled as the Brotherhood would turn out to be so incompetent in governing.
"Everything in Egypt is worse as a result of Morsi's policies," said Gerges. "His authoritarian ways, his economic mismanagement ... clearly they don't have ideas. It is basically an emperor with no clothes. The Islamist movement is naked. This will have major implications for movements in the region."
It was not just the vast crowds in Tahrir Square, the cradle of the revolution, that exploded in joy as the army commander Abdel Fattah al-Sisi told the nation on Wednesday that Morsi was no longer their president.
Crowds in Tunis, where the Arab Spring kicked off with the toppling of Zine El Abidine Ben Ali, converged on the Egyptian embassy to celebrate Morsi's removal, chanting "Today Egypt, Tunisia tomorrow. Down with the rule of the Muslim Brotherhood , down with the rule of Ennahda. It's a revolution until victory."
On Facebook, thousands of Tunisians rejoiced. The message to Ennahda leader Rachid Ghannouchi: "Morsi is gone and you Ghannouchi when?"
Analyst Sofian Bin Farhat said: "This is the fall of political Islam in Arab Spring countries after a catastrophic failure."
The writing was on the wall for Morsi, now being held at Egypt's defence ministry, when millions took to the streets on Sunday, the anniversary of his election, to demand he resign and accusing his Brotherhood of hijacking the revolution.
That gave army chief al-Sisi justification to invoke the "will of the people" and demand Morsi share power or step aside.
What was unveiled by the general was a plan to wipe clean a slate of messy reforms enacted since Mubarak fell. The constitution was suspended and the constitutional court chief justice, Adli Mansour, was sworn in to replace Morsi. An interim cabinet will be formed and the constitution will be reviewed. Presidential and parliamentary polls will be arranged.
NOT FOR MUSLIMS
Many in the opposition hope they will have more electoral success than last year. The Brotherhood's ability to mount a democratic comeback may be limited by the arrests of its leaders. They face accusations of inciting violence.
Morsi too may face charges. His opponents accused him this week of fomenting "civil war" by defying Sisi's ultimatum.
Events could influence the way Islamists view democracy, for some already a dubious Western import designed to keep them out of power. As Essam Haddad, a Morsi aide, wrote as the army coup unfolded, this "message will resonate throughout the Muslim world loud and clear: democracy is not for Muslims."
Jane Kinninmont, a Gulf expert at Britain's Chatham House, said the Brotherhood had over reached themselves in power and failed to listen to opponents.
"But the process of the military coup is deeply worrying... Being forcibly overthrown is not going to make them give up on wanting power, but raises major questions about future strategy, and if they come to think peaceful elections are not a credible option, that could be very dangerous," she said.
Analysts agree that the putsch against freely elected Morsi will have wider implications and poses a dilemma for Western governments supporting democracy.
"It is a full-fledged coup d'etat. It undermines the very foundations of the democratic process. It is a move fraught with risk and uncertainty. It shows that the opposition was not able to force Morsi out without the military. It deepens the divide in Egyptian society," said Fawaz Gerges.
Under a worst case scenario, the Brotherhood might decide to fight back. This could lead to a bloody confrontation with the army similar to Algeria's civil war in the 1990s when the military stepped in to deny the Islamists election victory.
The well-organised Brotherhood could mobilise once more and secure another victory at the next presidential elections, which would leave the military and the country in limbo once more.
Kinninmont said the Brotherhood's supporters would not turn against the organisation on the basis of one year in office.
"Now in the face of a military coup they'll be less likely to listen to any internal criticism, and their support base is likely to harden behind them. They have the numbers to mount massive protests and to affect the economy, even if they don't represent the majority of society," Kinnimont said.