Ahmadinejad's standing at home appears to have suffered since the election. Several Tehran newspapers reported that 185 out of 290 members of parliament, including Speaker Ali Larijani, stayed away from a victory celebration for Ahmadinejad on Tuesday.

Ahmadinejad's patron, supreme leader Ayatollah Ali Khamenei, has said the election result would not be reversed.

The fallout may leave Khamenei and the ruling theocracy battered by once-unthinkable defiance of their leadership. But they still control the Revolutionary Guard and its vast network of volunteer militias that watch every corner of Iran.

The Guard — sworn to defend the Islamic system at all costs — has been steadily expanding its authority for years to include critical portfolios such as Iran's missile program, its oil pipelines and other energy infrastructure, and some oversight of the nuclear program.

Iran's most senior dissident cleric, Ayatollah Hossein Ali Montazeri, warned the authorities that trying to snuff out dissent would prove futile.

If people are not allowed to voice their demands in peaceful gatherings, it "could destroy the foundation of any government," regardless of its power, wrote Montazeri. He was the heir apparent to the late Ayatollah Ruhollah Khomeini until falling out of favor with the ruling clerics by questioning their almost limitless powers. Montazeri spent five years under house arrest in the city of Qom, a center of clerical power and Shiite Islamic learning.

Laub reported from Cairo.