That ordinary Syrians have braved bullets and tanks to take to the streets for 18 consecutive weeks seeking the ouster of President Bashar al-Assad is an indicator of their movement’s resilience. Courage is one quality the protesters do not lack.

Just about every other ingredient that usually goes into building a revolution — organization, strategy or leadership — is still missing, however.

The nationwide uprising that erupted spontaneously on the streets of Syrian cities remains a largely ad hoc affair, inspired by the revolts in Egypt and Tunisia, driven by anger and frustration with decades of dictatorship, but lacking a clear direction or structure beyond the unanimous demand that Assad should go.

“This is the purest people’s revolution there ever was,” said a Damascus-based activist who is affiliated with two of the groups engaged in encouraging protests. Leaders are nonexistent, he said, and they wouldn’t be welcomed. “Anyone who puts his head above sea level is taken down,” he said.

As the weeks turn to months with no sign that either side is prepared to give way, the question of how the protesters will translate their momentum into concrete steps to replace the regime — and who will do it — is gaining urgency. The United States and other world powers are increasingly distancing themselves from Assad, while a growing number of think tanks and experts are becoming convinced that his regime will not survive.

At the same time, scattered incidents of sectarian violence in some protest flash points, such as the city of Homs, have focused concerns on the risk that the unrest in Syria could degenerate into chaos and civil war should the regime fall suddenly without a transition plan in place.

Officially, the United States is adopting a hands-off position, saying it is up to the Syrian people to determine their future. But behind closed doors, “a lot of people are obsessed with this issue,” said Andrew Tabler of the Washington Institute for Near East Policy. “As the regime degrades, the necessity of the opposition coming together grows.”

Efforts by exiled opponents of Assad to form a united front have faltered, in part because of an acute awareness that the Syrian street is driving the uprising. No one, least of all the Syrians, said a Western diplomat in Damascus, wants to see a repeat of the Iraq experience, in which exiled leaders with no street credibility are foisted upon those living inside the country.

Yet such is the severity of the crackdown that the real protagonists of this youthful revolt cannot gather to strategize, debate the way forward or select representatives. An attempt to link a conference of exiles in Istanbul with an assembly of domestic opponents in Damascus this month was abandoned because security forces surrounded the site and killed demonstrators the day before, making it too dangerous for participants to attend.

Youth activists inside Syria say that in any case they are too focused on organizing the protests while evading arrest to find time to address the future. Operating as tightly knit groups with names such as Trust Circle, the Syrian Creative Revolution and the Revolution of Syrian Youth, they communicate in code, know one another by fake names and exist largely on the Internet.

Countless such groups exist around the country, and while they say they do not compete with one another, neither do they coordinate. And even these groups acknowledge that they play only a minor role in fomenting protests, which are sustained for the most part at the local community level by the grievances of ordinary citizens, or by the convictions of people such as the young professional in Damascus who has participated every Friday since March in the demonstrations held in the central neighborhood of Midan.

Nobody tells him that there will be a demonstration, nobody encourages him to go. He just shows up with a group of friends, assuming there will be a demonstration because there always is.

“I'm really not political. I'm just a guy going to the streets every Friday,” he said in an interview conducted over Skype, when asked which of the various protest groups he supports. He hasn’t heard of any of them. “I only want to end the injustice and see a free democracy,” said the man, who requested that his name not be used because he fears for his safety should he be identified.

There is a small community of established, mostly elderly dissidents who have long opposed the regime, who served time in prisonand who could yet emerge as potential leaders of a new Syria. They are keeping a low profile, mindful that this is not their revolution.

The two activists with the most name recognition inside the country are women: Razan Zeitouneh, a human rights lawyer who has often spoken out from hiding in Damascus on behalf of the Local Coordination Committees, the best known of the various groups opposing the regime, and Suhair Atassi, a veteran activist who leads the Syrian Revolution Coordination Union.

Even these groups are regarded with skepticism by many protesters, said Damascus- based activist Abu Adnan, who works with two groups. “They are fake groups, they exist only in the media,” he said. “People are suspicious of those who want to take personal advantage from the revolution.”

Indeed, most activists reject outright the notion that anyone should take charge of a revolt dedicated to the overthrow of the only form of leadership most Syrians have ever known.

“The people who are on the streets don’t want a leader,” said Dhia Aldeen Dugmosh, 25, a protest organizer who was detained twice and escaped to Beirut. “Not only the Syrian people, but all the Arab people, are fed up with having a leader. It would create dissent and fragmentation.”

Some say they realize they need to plan, including Rami Nakhle, a Beirut-based founder of the LCC, which has emerged as the most high-profile and influential opposition group primarily because it has effectively reached out to Arabic and Western media.

He has created what he calls a virtual parliament comprising representatives from Syria’s provinces, who meet online to debate how a transition might be managed. He is also reaching out to some of the exiled dissidents, including the academic Burhan Ghalioun, who is admired in part because he has asserted no political ambitions, to try to forge a united front.

But anointing leaders would be counterproductive for a revolt that has demonstrated a high degree of cohesiveness without formal guidance, he said.

“It’s a very important question for the international community but not for the Syrian people,” Nakhle said. “The international community wants to know who will take over, will they be Islamists and so on. We say, democracy will take care of that.”