BEIRUT, Lebanon — On the night that Libyan rebels poured into the citadel of Col. Muammar el-Qaddafi, inaugurating Libya’s future, his counterpart in Syria offered assurances borrowed from the past: Syria would stay steadfast, plots hatched from abroad would fail and calls for his removal were meaningless because the people supported him.

“I am not worried,” President Bashar al-Assad declared in a television interview on Sunday.

But with the end of Colonel Qaddafi near and rebellions elsewhere in the Arab world either repressed or dangerously anarchic, the uprising in Syria emerges as the front line of the Arab revolts. In eight months, three strongmen have fallen in a region renowned for decades for its leaders dying on their thrones. While Libya and Syria have little in common beyond their repression, the arithmetic of the region seems to be betting against authoritarian rule that fails to reform.

“The change taking place in Libya in compliance with people’s demands, following what happened in Egypt and Tunisia, should teach a lesson to everyone,” the Turkish foreign minister, Ahmet Davutoglu, said Monday in Ethiopia, in a thinly veiled reference to Mr. Assad. “Leaders of other countries must also be aware of the fact that they will be in power as long as they satisfy the demands of the people.”

Jubilation, fascination and a hint of disdain at the Libyan rebels’ reliance on Western power reverberated through the Arab world Monday, as scenes were broadcast of rebels in Tripoli’s Green Square. “Victory” was a word heard about the end of a figure seen by many as despotic and unhinged; a line from a speech early on by Colonel Qaddafi, when he vowed to fight “zanga zanga,” or alley to alley, became a pop culture reference and was mockingly introduced as a new phrase into colloquial Arabic.