Gary Sick, who was the chief White House aide during Iran's Islamic Revolution in 1979 and the hostage crisis that followed, says the Green reform movement has a surprising strength. Tens of thousands of protesters have taken to the streets of Iran Thursday.
Top opposition candidates, including defeated presidential candidate Mir Hossein Mousavi, are among those who may be targeted.
Growing unease over conditions of detention for hundreds is helping opposition organize, and exposing some splits in Iran's conservative ranks.
After stamping out election protests, Iran may see its "resistance" brand weaken. The first big test: The Non-Aligned Movement summit, which opens Wednesday in Egypt.