The demographics of Iraq are broadly constituted by the Shia, Sunni, and Kurdish groups. The Shia sect is in the majority, forming almost 65% of the population, with the Sunni sect forming a significant minority comprising as much as 30% of the population. However, under the Sunni leader Saddam Hussein's rule, the Sunni minority became the politically powerful class, with Hussein deprioritizing the Shia majority. Post the American Occupation of Iraq in 2003 that deposed Hussein, Iraq's political order has functioned through the Muhasasa system in an attempt to provide proportional representation to Iraq’s various ethno-sectarian groups in cabinet positions.
Under the Muhasasa system, Iraq's political system functions on a "spoils basis" for the distribution of government jobs, offices, and perks. A spoils system is a practice in which a political party — after winning an election — rewards its supporters, friends, and family for its victory with these perks to further incentivize them to work for the party.
Critics have pointed out how the Muhasasa system led to the recentering of power within a tight coalition of Shia parties, with residual influence being shared with Sunni and Kurdish groups.
Over the years, this arrangement has made Iran, another Shia-majority state, an important presence in Iraq's politics as the sponsor of Shia parties.