Grand Ayatollah Ali al-Sistani has been here before.

Fifteen years ago, after the US-led invasion of Iraq had toppled the dictatorship of Saddam Hussein, the country’s most senior cleric helped guide his people towards a system of representative government.

Now, having himself helped to topple the latest iteration of that government, Sistani knows his flock is again looking to him for political guidance.

He does not relish the responsibility. Sistani, 89, represents the “quietist” school of Shiite Islam, which takes the view that senior clerics must not dabble in politics. For much of his adult life, he has argued against the notion of “vilayat-e-faqih”, or rule by the Islamic jurist, promoted by Ayatollah Ruhollah Khomeini and practised in Iran since the 1979 revolution.

But the dire political circumstances in Baghdad may require Sistani to take on a more active role than he would like.

Sistani has said Iraq needs fresh elections and wholesale constitutional reforms, but has been careful to avoid suggesting specific changes. That, in his view, is the business of the country’s political class.

But there’s the rub. Iraq’s politicians have demonstrated little interest in change, and Sistani himself bears some responsibility for the dysfunction that has come to characterise the country’s parliament. Every government since the fall of Saddam has had his blessing; every prime minister has sought and received his approval. The latest premier, Adel Abdul-Mahdi, a man with no party or constituency of his own, could not have got the job without Sistani’s benediction.

Though Iraqis might reasonably begrudge Sistani for the incompetence and venality of their political elite, they seem inclined to give him the benefit of the doubt, not least because of his personal probity and the prestige of his office, which is arguably the highest in Shiite Islam.

But the protesters who have kept up pressure on the government for weeks on end — braving bullets, teargas and truncheons — may lose their patience with Sistani if he remains in his comfort zone, on the sidelines.

It may take all of the ayatollah’s clout to offset the Iranian influence on Iraqi politics. Tehran has already dispatched its formidable enforcer, Maj-Gen Qassem Soleimani, to participate in the negotiations over Abdul-Mahdi’s departure.

It is likely to take more than Sistani’s personal prestige to keep Soleimani at bay. In the rough-and-tumble world of Baghdad politics, where parties routinely use militias for leverage, Iran can call on a wide array of armed groups. Tehran’s politician of choice is Hadi al-Amiri, who commands the Badr Organisation, which is both a paramilitary and a political party.

Amiri’s only rival for political power is the cleric Moqtada al-Sadr, who has positioned himself as an Iraqi nationalist. Both men are Shiites, but Sadr’s nationalist credentials give him traction with the Sunni minority, which is distrustful of Amiri’s Iranian ties. Sadr’s militia is the Mahdi Army, which makes up in numbers what it lacks in firepower and discipline.

In political terms, Sadr and Amiri cancel each other out. Sistani has previously avoided endorsing either of them, preferring Abdul-Mahdi as a compromise. It was a disastrous choice: Abdul-Mahdi had neither the political nous to manage a fractious parliament nor the administrative skills to run the country.

Even if parliament heeds Sistani’s call for constitutional reforms, Iraq will need an interim leader. And so, again, the ayatollah faces the choice of Sadr and Amiri. Backing the leader of the Badr Organisation would amount to putting Iraq firmly under Iranian control, betraying the aspirations of the protesters. Though of Iranian descent himself, Sistani has in word and deed been loyal to Iraq.

But taking sides with Sadr will not sit well with Sistani, either. The younger man is unpredictable and given to violent outbursts; he has articulated no coherent vision for what Iraq ought to be, much less a plan to fix its economic and political problems. There is no reason to believe he — or anyone from his party — will make a good administrator, especially at a time of national upheaval.

Sistani’s preference will be to wait for another compromise candidate to emerge. But that cop-out may no longer be available: the protesters are in no mood for a long, drawn-out political process. And it may well be that there are no untainted politicians left in Baghdad.

• Ghosh is a columnist and member of the Bloomberg Opinion editorial board.