Notable by his absence from this week's gathering of the U.N. General Assembly is Syria's president, Bashar Assad. The Syrian leader had hoped to attend, and he was even said to be weighing television interviews for himself and his stylish, British-born wife. His decision to stay home indicates the disarray in Damascus these days.

"Fear has changed camps," says one senior official involved in Syria policy. "In Damascus, fear is now in the camp of power, the camp of Bashar." That represents a stunning change after several decades in which the Baathist regime maintained control at home and in Lebanon through raw physical intimidation.

The tourniquet that is tightening inexorably around the Assad regime is the U.N. investigation into the murder last February of former Lebanese prime minister Rafiq Hariri. That probe, headed by a relentless German prosecutor, Detlev Mehlis, has already turned up enough evidence to arrest four security chiefs of the old Syrian-backed regime in Beirut for possible complicity in Hariri's death. Mehlis was in Damascus this week seeking testimony from top Syrian officials.

Analysts believe that Assad canceled his New York trip for two reasons: U.S. officials couldn't guarantee his entourage immunity from arrest if Mehlis and the Lebanese government issued a warrant, and, more important, he feared the risk of turmoil in Damascus if he were to leave now.

What an invigorating spectacle, to watch as the rule of law squeezes the arrogant men who treated Lebanon as their private fief. Some of them are in jail; others are trying to cut deals; still others are said to have defected to other countries. Credit goes to Lebanon's new government, which was tough and united in making the surprise arrests, at dawn on Aug. 30, of the security chiefs. Rumors are spinning in Beirut and Damascus about which members of the Assad regime are ratting out their friends. A Paris-based newsletter, Intelligence Online, wrote that a Syrian intelligence colonel had defected to France with information about the Slovakian-made explosives that allegedly killed Hariri. Another online newsletter, DEBKAfile, identified the intelligence defector with a different first name and said he "supplied his French intelligence interrogators with the names of colleagues directly complicit in the assassination."

The rumor mill is also churning with speculation about whether any of the Lebanese security chiefs might be cooperating with prosecutors. One of the four, Maj. Gen. Jamil Sayyed, is known to have recorded many of his important meetings. There's also speculation that Hariri himself may have recorded a meeting with Assad just before his death, in which the Syrian leader is said to have threatened Hariri with dire consequences if he didn't change his anti-Damascus stance. Among Syria-watchers, there's a guessing game now about which generals and politicians may be ready to jump ship. "You sense the disarray in Syria these days," says Emile Hokayem, a Lebanese-born analyst with the Henry L. Stimson Center in Washington. Many analysts think Assad would probably give up one of his intelligence chiefs if that were the price of his own political survival.

The Bush administration is debating whether to try to accelerate this unraveling with an explicit policy of regime change. President Bush is said to have expressed frustration with the conventional wisdom -- that the only alternative to Assad and his Alawite clan is rule by Sunni fundamentalists from the Muslim Brotherhood -- and asked his aides to explore alternatives. Soon after, a top Middle East expert on the National Security Council staff met for the first time with Farid Ghadry, head of a Syrian opposition group in exile. Ghadry told me he plans to convene by year's end a parliament in exile that would include all strands of the Syrian opposition, including those in the Muslim Brotherhood who are ready to embrace democracy. He said he has also quietly signaled Alawite tribal leaders that their sect could maintain control of the military during a political transition, avoiding the bloodbath the Alawites fear.

The administration would make a mistake, in my view, if it moved openly now to topple Assad. The mess in Iraq is a potent warning about the dangers of kicking over hornets' nests. And what's the rush? Right now events are taking their course. A U.N. prosecutor is on the road to Damascus, following the trail of evidence. The scoundrels are running for cover. The Assad regime appears to be caught in a trap of its own making, and every day the balance of fear will tip a little farther.