Ayatollah Khomeini may have founded Iran’s Islamic Republic in 1979, but for the regime in Tehran, his revolution has never really ended.  Iranian politics remain a vortex of factional struggle as hardliners and reformists compete to shape the regime’s character.  American diplomats have long cheered the reformists believing that should reformists triumph, Iran might moderate and return into the family of nations.

In reality, however, the struggle between reformists and hardliners is more style than substance.   Both embrace Iran’s nuclear program, support terrorist groups, and violently oppose Middle East peace.  Mahmoud Ahmadinejad, Iran’s hardline president, shocked the West with his virulent Holocaust denial, but his reformist predecessor Mohammad Khatami embraced Holocaust denial, just more quietly.

The Islamic Republic’s true Achilles’ heel is not factionalism, but rather the Shi‘ism upon which it is based.  Shi‘ite Muslims embrace a religious hierarchy somewhat analogous to that in Roman Catholicism but instead of having cardinals select a single pope, every Shi‘ite picks his own personal pope from amongst the leading ayatollahs.  Shi‘ites then show their allegiance by paying religious taxes to the ayatollah they embrace.

Here’s the problem:  Ali Khamenei, the leader of the Islamic Republic, calls himself the Supreme Leader and claims both ultimate political and religious authority.  Most Shi‘ites don’t buy it.  Not only do most Iranians not pay their religious taxes to the Supreme Leader — preferring instead more moderate ayatollahs in Iraq — but the Iraq-based ayatollahs daily contradict Khamenei.  This creates a crisis of legitimacy for Iran.

Every Iranian knows that Iran has faced two major, violent revolutions in the 20th century:  seven decades before the Islamic Revolution, there was a constitutional revolution.  In both cases, clerics in Iraq helped coordinate the opposition.  Simply put, a free Iraq is kryptonite for Iran’s leaders.

Khamenei’s strategy is to suppress Iraq with militias.  He seeks to impose through the barrel of a gun what isn’t in Iraqis’ hearts and minds. Khamenei wants a compliant little brother, not a democracy next door.  Last year, three different grand ayatollahs told me they feared an American departure would mean a repeat of 1991.  Then, a precipitous withdrawal foreshadowed bloodshed, dictatorship and, ultimately more war.

The next American administration faces a number of decisions.  Can the United States afford to let Iraq slip into Iran’s shadow?   If so, might the American withdrawal strengthen Iran’s hardliners?  Alternately, if Iraq is too important to accept Iranian dominance, how can the United States help Iraq resist Iran without boots on the ground?

Michael Rubin is a resident scholar at AEI