When popular rebellions began erupting around the Middle East earlier this year, the outpouring of democratic fervor was quickly dubbed the Arab Spring, a phrase that captured the heady optimism of what appeared to be a new era of freedom and hope.

But as spring turns to summer, events across the region are taking an altogether darker and more sinister turn, one in which the prospect of a brighter future no longer seems so readily assured.

The swift toppling of the presidents of Tunisia and Egypt, in rapid succession, has been followed by months of deepening bloodshed and brutality across the Arab world, underscoring the power that autocrats still wield after decades of dictatorship.

“We’re rapidly coming to a fork in the road, where one path leads to change and reform and the other leads to retrenchment and repression,” said Salman Shaikh, director of the Brookings Doha Center in Qatar. “It’s going to be a long and bloody haul, and it could take us over a number of years.”

The tiny kingdom of Bahrain has been the first to point the way to a different outcome, having decisively crushed its popular uprising with the help of Saudi troops. Now, human rights groups say, authorities there are engaged in a systematic persecution of the mostly Shiite majority that dominated the demonstrations earlier this year.

In Syria, the government headed by President Bashar al-Assad is pursuing a remorseless effort to quell a pro-democracy movement, using tanks and artillery to pound neighborhoods that had participated in demonstrations, and detaining by the thousands whole communities of young men. A crucial test could come Friday, the usual day of protests, as authorities watch to see whether the extraordinary repression of the past week will finally succeed in suppressing the revolt.

In Libya, where Moammar Gaddafi was the first to unleash the full force of the state against his citizens, an all-out war is raging in which NATO fighter jets are taking the lead. In Yemen, a bloody stalemate continues to regularly claim the lives of demonstrators seeking the ouster of President Ali Abdullah Saleh, who is stubbornly resisting multiple efforts to persuade him to leave.

In Egypt, deadly sectarian clashes between Christians and Muslims in Cairo have come as a sobering reminder that negative as well as positive forces may be unleashed by the removal of dictatorial governments. And even in little Tunisia, which first heralded possibility of change when its president was forced to flee in January, elections promised for July are in doubt and street protests have continued as frustrations build because of the slow pace of change.

Yet, although governments may succeed in the short term in holding on to power, few think it likely or even possible for the region to revert to its former self.

“Things cannot go back to the way they were before,” said Jordanian political analyst Labib Kamhawi. “We’ve seen a fundamental shift. People have seen freedom, and there is no turning back.”

When President Obama delivers a major address on the Middle East next week, ostensibly to mark the capture of Osama bin Laden, many in the region will be hoping to hear a more decisive condemnation of the levels of force being used against protesters, said Nadim Shehadi of the London-based Chatham House think tank.

On Thursday, Secretary of State Hillary Rodham Clinton suggested that the United States is considering a more robust response to the crackdown in Syria, after weeks of little more than verbal condemnation. “We are going to hold the Syrian government accountable,” she said during a visit to Greenland.

“Syria’s future will only be secured by a government that reflects the popular will of all of the people and protects their welfare,” Clinton said, while still stopping short of calling for Assad to step down.

But no matter what steps the United States takes, the reversals of the past three months suggest that the Middle East is destined for a prolonged period of instability, the end result of which cannot be foretold.

The regimes still battling to hold popular revolts at bay have warned that change could open the way to Islamist extremism. But some analysts warn that radicalization could just as easily occur if the authorities succeed in crushing the peaceful and spontaneous demonstrations demanding democracy.

“If these Arab revolutions do become a footnote, and if people do become frustrated and see no light at the end of the tunnel, I don’t know where it could lead in terms of people thinking of al-Qaeda” or otherwise taking up arms to fight, Shaikh said.

Syria is being mentioned as a candidate for civil war, with or without the Assad regime. The Assad family has been in power for 40 years.

With chants of “peaceful, peaceful”’ at nearly every demonstration, activists in Syria have insisted that they do not want their country to follow the path of Libya toward armed conflict and international intervention. But Syria also lies in a dangerous neighborhood, wedged between Iraq and Lebanon, where weapons are abundantly available, and there have been numerous reports that arms are starting to find their way across both those borders.

In Bahrain, too, the levels of repression by the Sunni monarchy have included the razing of Shiite mosques and the beating and detention of schoolgirls who joined in demonstrations. Analysts say that Shiites there could be driven over time toward the more extremist ideology of nearby Iran.

So dizzying have been the changes unleashed across the region in just a few short months that the world’s hesitant and seemingly inconsistent response to the upheaval can be understood, said Rami Khouri of the American University of Beirut. And so, too, he said, should the missteps and lapses of the region be forgiven, as it lurches into uncharted territory toward what many there still fervently believe is an irrevocable future.

“This is widespread, it’s sincere, and it cannot be put back in the bottle,” Khouri said. “We just have to be realistic about time frames. I’m not saying it will take us 800 years, like it took you in the West, but at least we need more than a few months.”