The United Nations Security Council is debating what, if anything, to do about Syria, as President Bashar al-Assad's crackdown on protesters enters a new, more violent phase. Scores of tanks and armored vehicles are amassing near the northern town of Jisr al-Shoghour, most of whose residents have reportedly fled to nearby Turkey or elsewhere. The military buildup is the result of a disputed government claim that terrorists had killed 120 soldiers in the town on Monday. Is Assad losing his grip on power? Here, three reasons he may be on his way out:

1. The coming massacre in the north will be the final straw
Thousands of elite Syrian troops are heading toward Jisr al-Shoghour, but "Assad must be wondering if this all-out military effort to quell the 11-week popular uprising will be his last," says Patrick Martin in The Globe and Mail. As Syria expert Barry Rubin says, this "looks like the tipping point," and Assad faces the real possibility that this "drastic action" will just fuel the broader uprising, and might even spark a coup. Indeed, "a really savage crackdown will seal the fate of the Assad regime," says Gideon Rachman in the Financial Times.

2. Assad is losing the army
There are reports that growing numbers of soldiers are defecting to the opposition. "In all likelihood, there will be growing defections as the fighting gets worse," says Joshua Landis at Syria Comment. The army could even "split along sectarian lines," leading to full-fledged civil war. Plus, says Esther Adorno at Harper's, "soldiers are being killed for refusing to shoot civilians," and some are fleeing to Turkey.

3. An economic collapse will anger his supporters
So far, at least, the revolutionary fever hasn't spread to the "content urban upper class that has benefitted from the Assad rule," says Chris Keeler at Notes From a Medinah. But "a collapse in financial markets could push the merchant classes in Damascus and Aleppo to join the protesters," says The Washington Post. And the violence and instability are bringing Syria's economy to its knees. "The death of tourism is the most visible sign of major economic damage from the protests and crackdowns," but that's just the tip of a very ominous iceberg for Assad.