Ever since Tunisian fruit seller Mohammed Bouazizi set himself ablaze 86 days ago, the Arab uprising has been a mutating virus. That is why Moammar Gaddafi — who has set Libya ablaze — has become so important.

By now it’s almost hard to remember, but Bouazizi at first inspired not popular protests but copycat self-
immolations in Algeria and Egypt. Then the contagion altered: A mass secular movement emerged in Tunisia under the banner of liberal democracy, and Egypt’s young middle class took up the same cause. U.S.-allied armies in Tunisia, Egypt and Bahrain decided one after the other that they would not gun down their own people to preserve the autocratic status quo — and each decision strengthened the principle of nonviolence being pushed by the United States and other outside powers.

Now Gaddafi has altered the virus’s nature once again. Thanks to his “Green Book” madness, Libya stood for decades at the margins of Arab politics. But Gaddafi’s scorched-earth campaign to save himself has not only stopped and partially reversed the advance of rebel forces on Tripoli during the past two weeks; it has done the same to the broader push for Arab democracy. If he survives, the virus of repressive bloodshed and unyielding autocracy could flow back through the region.

Maybe it already has. Egypt has seen dangerous outbursts of violence the past couple of weeks, including sectarian clashes between Muslims and Christians. Security forces in Yemen have attacked crowds in the capital, Sanaa, with live ammunition twice in the past week, and violent clashes have resumed between security forces and protesters in Bahrain.

Pro-democracy forces outside of Egypt and Tunisia have stalled. Algeria and Morocco have gone quiet. In Saudi Arabia on Friday, a “day of anger” advertised for weeks on Facebook failed to produce a significant turnout. And there has been no sign of rebellion in the Arab country whose dictatorship rivals Gaddafi’s for ruthlessness: Syria.

In Egypt, to be sure, liberal forces remain strong. Though still relatively disorganized, the youth-led movement immortalized in Tahrir Square pushed out the prime minister and cabinet left behind by Hosni Mubarak and ransacked the headquarters of his once-feared secret police. Two credible candidates for president, former Arab League secretary general Amr Moussa and former U.N. nuclear inspector Mohamed ElBaradei, have stepped forward, offering the prospect of genuine democratic competition and an outcome that Egypt’s neighbors and allies can live with.

But some Egyptians think the country is dangerously close to unraveling. “We may never get to the presidential election,” said one well-informed source I spoke to. The economy, he said, remains stopped; the government may soon run out of cash to pay salaries. Authority of all kinds is crumbling: Factory managers and union leaders are being challenged by their rank and file, and police have largely disappeared from the streets.

This Egyptian had a troubling thought: “What if Libya had happened first?” he wondered. “What would have happened then in Egypt?” The obvious follow-up question: In a Middle East where one dictator is slaughtering his way to at least temporary safety, what might the remains of Egypt’s autocracy be tempted to do if the country’s disorder grows? The country’s new reformist prime minister, Essam Sharaf, clearly has been thinking about this: Last week he warned that an “organized, methodical counter-revolution” was already underway.

What if Gaddafi were defeated and deposed? Naturally, this would not solve Egypt’s problems or cause the Assad dictatorship in Damascus to crumble. It would, however, cause the Arab virus to mutate again. It would give new strength to the idea that the Arab dictators can no longer save themselves through bloodshed. It would probably encourage more pro-democracy uprisings.

And what if Gaddafi’s downfall is brought about, in part, through military assistance from France, the United States or other Western powers — arms deliveries or a no-fly zone? Some seem to think this would weaken the Arab revolutionaries, by introducing a foreign element. More likely it would do the opposite. Just ask a leading opponent of intervention, Post columnist George F. Will.

“The Egyptian crowds watched and learned from the Tunisian crowds,” Will observed last week. “But the Libyan government watched and learned from the fate of the Tunisian and Egyptian governments. It has decided to fight. Would not U.S. intervention in Libya encourage other restive peoples to expect U.S. military assistance?”

The answer is: Perhaps it would. And: If a powerful opposition movement appeared in Syria, and asked the West for weapons or air support to finish off the Assad regime, would that be a disaster?