As Iraq remains gripped by violence and political turmoil, Shia leader Muqtada al-Sadr is once again mobilising Iraqis against the government on a scale that is unprecedented in Iraq's recent protest movement.

Considered one of the most influential people in the country, Sadr leads a populist movement, controls one of the biggest political blocs in parliament and commands a powerful militia. The 42-year-old is also viewed as a champion of Iraqi nationalism, enthusiastically working with a cross section of Iraqi intellectuals to help forge a national unity platform to reform Iraq's fundamentally flawed governance.

Sadr, however, remains a controversial figure. Soon after he launched his Sadrist Movement, following the US occupation of Iraq in 2003, Sadr was accused of being a destabilising force and a divisive figure who stoked sectarian tension.

Even after Sadr transformed himself into a statesman, many believed that he became part of the Shia oligarchy whose political factions were part of the corrupt and inept establishment that has put Iraq into a dire state.

Still, Sadr's power is undeniable, with his grassroot party that expands working-class neighbourhoods across Iraq's Shia-populated cities and its al-Salam Brigades paramilitary force, he is the most powerful Shia leader by far.

READ MORE: Iraq's popular demobilisation

On Friday, Sadr led one of the biggest protest rallies in Iraq's modern history. Tens of thousands of Iraqis took to the streets of Baghdad to demonstrate against corruption and the government's backtracking on reform plans, as called by al-Sadr.

Fixing Iraq's broken politics requires more than a change of government. It needs first and foremost abandoning of the political system forged by the US occupation authority which has strengthened the hands of a sectarian and ethnic oligarchy.

The protesters, who gathered in Baghdad's central Tahrir Square, waved Iraqi flags and chorused that they would fight "corruption and corrupts" in the government.

Speaking on a stage, Sadr told the crowd that they should be prepared to continue their protest movement until Prime Minister Haider al-Abadi met demands to implement "fundamental" reforms.

The rally ended with a warning that the protesters would storm the Green Zone, the fortified area in Baghdad which is host to government headquarters including Abadi's offices, if the prime minister failed to carry out the required reforms.

The march was a working portrait rich with evidence of what kind of a political leader Sadr might be, and especially of his expansive and muscle-flexing approach to Iraq's lingering crisis.

There are two main reasons behind Sadr's new confrontational rhetoric which explain his strategy to consolidate his power base among Shia while adopting a strategy that transcends sectarian interests.

First is a Shia power struggle. In recent weeks, Shia factions have been bickering over competing claims and ambitions to run the government. The row grew out of the reforms that Abadi has pledged to carry out in response to widespread protests that have taken place since August against rampant government corruption and poor services and in favour of calls for change.

The conflict intensified after Abadi declared that he wants to replace politically appointed members of his cabinet with professionals and technocrats in an effort to push his reform programme.

Shia political elites who dominate the government and the parliament have resisted Abadi's reforms, though too meagre to matter.The Shia National Alliance has insisted that the present quota-sharing system that distributes seats in the government according to sectarian and ethnic quotas should remain in place.

Sadr's populist drive is clearly aimed at Abadi and his Dawa Party. He believes that Abadi's plans for a government reshuffle that will exclude politically affiliated ministers will only benefit his rival Dawa Party as it will keep Abadi at the helm of the government.

The second reason behind the resurgence of Sadr's anti-government fervour is the rise of the Shia militias. Sadr, who rose to prominence during the US occupation of Iraq, has capitalised on patriotism to launch his Jaish Al-Mahdi (Al-Mahdi Army) militia to oust the Americans.

The surge of dozens of Shia militias following the advances of the Islamic State in Iraq and the Levant (ISIL) in summer 2014 has made Sadr felt threatened by the muscle-bound rivals who have entered the ring.

Sadr's main worry is that with the resurging militias and their jaw-dropping performance in the war against ISIL, his Sadrist Movement with its armed wing will no longer be the only truly player on Iraq's Shia stage.

OPINION: Endless battle - fighting systemic corruption in Iraq

Last month Sadr's followers clashed with members of Asa'ib Ahl al-Haq (AAH), one of the key groups comprising the Shia-dominated popular mobilisation forces fighting alongside the Iraqi army, in several Baghdad's neighbourboods and other towns.

AAH supporters tore down Sadr pictures after he called for militias, including his own, to be absorbed into the Iraqi army.

But Sadr's main concern is that these militias may fight him over influence and authority in his traditional constituency; the poor and disfranchised Shia following their successes in the war against the Islamic State.

Sadr's worst nightmare is that these militias will obtain enough votes in the next election to rival the power and influence of his al-Ahrar bloc in parliament that enjoys 34 seats.

As the massive rally on Friday has underlined, Sadr's status remains fundamentally vigorous when compared with other Shia factions that are blamed for Iraq's broken political system and its failing state.

In order to place his movement on a more solid footing for the future, Sadr has taken some shrewd tactical steps to pose as the nation's savior.

By moving to Baghdad from his stronghold in the Shia holy city of Najaf and resorting to active street politics, Sadr is adjusting actions to energise his movement and to stay close to popular discontent with the government. One of his first moves in Baghdad was to form a committee of secular, Shia, Sunni and Kurdish intellectuals and academic entrusted with the task of suggesting government reforms.

His aim is to reach out to all of Iraq's divided communities by presenting an alternative vision about the country's key political, security and economic challenges.

This week Sadr instructed al-Salam Brigades, his militia, to be ready for deployment to protect Baghdad after a major ISIL assault on the outskirts of the capital.

He also ordered two of his ministers and a former deputy prime minister to surrender to the judiciary after they have faced corruption charges.

On Monday he urged supporters to show up at the Green Zone's gates next Friday to "make your voices heard" to demand implementing his proposed "fundamental" reforms.

Sadr probably thinks his movement could emerge unscathed from the government's crisis and he emerges as Iraq's strongest Shia leader.

Yet the plain fact remains that the Shia religious factions, that came to power following the US invasion in 2003 that ousted Saddam Hussein's secular regime, have been largely responsible for turning Iraq into a broken country, a dysfunctional state and one of the most wretched places on the planet.

Fixing Iraq's broken politics requires more than a change of government. It needs first and foremost abandoning of the political system forged by the US occupation authority that has strengthened the hands of a sectarian and ethnic oligarchy at the expense of creating a true and genuine secular democracy, free of ethnic and religious strife.