What was a political divide has become a schism. Many Iranian leaders served time together in the shah’s jails; today, their visions of the Islamic republic differ so sharply that reconciliation would be almost impossible.

What happens next will be determined by three factors: leadership, unity and momentum…

Momentum may be the decisive factor. The regime will need to shift public attention to President Mahmoud Ahmadinejad’s second-term agenda. Though Ahmadinejad blames the outside world for the protests, he may focus on regional or international goals to win the legitimacy that his presidency is unable to get at home.