ABU DHABI, United Arab Emirates — Moktada al-Sadr, the maverick Shiite cleric, who contested the Iraqi elections on an inclusive, nonsectarian list with Communists, independents and liberal civil society groups, has emerged as the winner.

Mr. Sadr’s electoral list, “Sairoon” in Arabic, or “On The Move,” garnered the largest number of votes, although 56 percent of Iraq’s voters stayed away from the polling booths. During the campaign, Mr. Sadr promised to fight corruption, work across sectarian lines and bring in technocrats to run the government.

Prime Minister Haider al-Abadi’s list didn’t secure the top place in the elections. Baghdad did not vote for Mr. Abadi, but his electoral list gained support in Mosul, the city most devastated by the Islamic State and liberated under his leadership. Despite the loss of votes, Mr. Abadi bolstered his reputation, as the election was fair and nobody accused him of fraud, intimidation or abuse of power.

But a majority of the voters staying away from polling booths is a clear rejection of the system that has failed to deliver peace and security, let alone prosperity. Elections in Iraq are often followed by messy and long negotiations between coalition partners.

Mr. Sadr, who doesn’t have enough numbers to form the government alone, is likely to choose Mr. Abadi as his coalition partner for a new government. Mr. Abadi, whose list is among the top five winners in the elections, gracefully accepted the results — a rare gesture — and promptly congratulated Mr. Sadr on his success.

An alliance between Mr. Sadr and Mr. Abadi would move Iraq toward a more stable, inclusive and less corrupt state of affairs. It would reduce Iran’s grip on the country and create a more balanced set of relations with its neighbors.

Hadi al-Ameri is Iran’s preferred candidate to lead a new Iraqi government. Mr. Ameri heads the Badr Organization and is one of the leaders of the Popular Mobilization Forces, dominated by Tehran-backed militia groups, who fought the Islamic State along with the Iraqi military. He transformed the battlefield gains into the second-largest number of votes for his electoral list.

Mr. Sadr has publicly spoken about the need to disarm the P.M.F., called for integrating its elements into Iraqi official forces, and repeatedly rejected the notion of Iraq having “two armies.” A nationalist who has been a vocal critic of Iran’s role in Iraq, Mr. Sadr has stated in a number of interviews with Iraqi local media that Iraq “must remain free of our neighbor’s ambitions.”

While Mr. Sadr has a checkered past, including violence by his Mahdi Army, his new alliance and political positions seem to be the best option for Iraq. An alliance between Mr. Sadr and Mr. Abadi could move Iraq toward a more stable, inclusive and less corrupt state of affairs. Both have steered clear of the corruption that plagues many of those in power in Iraq. Mr. Abadi has experience in government, is known globally and has proven to be a capable politician. Mr. Sadr has wide popular appeal and can provide legitimacy to efforts against corruption.

Both have support from a Shiite Islamist base. Both have pledged to have technocrats in ministerial posts, a necessary move to get Iraq’s ministries to function and deliver services and not serve as mere sources of patronage for various political parties. They would also need to ensure that their alliance is inclusive, both in terms of gender and ethnicity, to expand their appeal.

Mr. Sadr and Mr. Abadi are Iraqi Islamist leaders who are vehemently Iraqi first. They are not focused on their Shiite identities and have remained largely free of Tehran’s control. The United States and the Arab states should seize the opportunity and support them. Mr. Abadi could help build a new relationship between Washington and Mr. Sadr, who fought American forces after the invasion and had an arrest warrant against him in 2003.

Saudi Arabia’s minister of state for Gulf affairs, Thamer al-Sabhan, was quick to welcome Mr. Sadr’s ascendance. Last year, Mr. Sadr visited both Saudi Arabia and the United Arab Emirates and met with the Saudi crown prince, Mohammad bin Salman, and the Abu Dhabi crown prince, Mohammed bin Zayed. Mr. Abadi made a point of reaching out to Arab states during his tenure. A government led by Mr. Sadr and Mr. Abadi can build on the initial engagement with Arab states.

Saudi Arabia and the U.A.E. have committed billions in reconstruction aid to Iraq. A new government in Iraq can work toward attracting investments from Saudi Arabia and the U.A.E. to boost private sector growth, which is crucial to economic diversification in Iraq.

Mr. Abadi could potentially help maintain a delicate balance between the regional rivals, as he has supported building ties with Arab countries while maintaining relations with Tehran.

Iran immediately sent Gen. Qassem Soleimani, the commander of the Quds Force, to Baghdad after the results, to ensure that its influence does not ebb with the formation of the next government. Mr. Ameri is maneuvering with his colleagues and allies such as former Prime Minister Nuri Kamal al-Maliki to form a government of Shiite Islamist parties, a move that would push Iraq back into the sectarian rut.

Mr. Sadr’s strong performance ensures that Tehran cannot have a new Iraqi government entirely beholden to it. Iran-backed P.M.F. and their allies will seek to carve out a position of power, emulating Lebanon’s Hezbollah. The P.M.F. has rejected efforts to be integrated into Iraqi forces. They want to remain a separate institution, keeping their arms while wielding political power as a bloc in Parliament, where they can use “veto power” to stall, block, and thwart legislation to cripple the government — another lesson learned from Hezbollah.

The supporters of Mr. Maliki and the P.M.F. could also demonstrate their opposition to a Sadr-Abadi coalition government on the streets, which carries the inherent danger of a new wave of violence.

There are further security challenges a new Iraqi government would face. Iraq’s Kurdish Autonomous Region is still reeling from the fallout of the ill-advised independence referendum. There have been accusations of fraud and voter intimidation and there are increasing fears of unemployed young men in the region turning violent. Any new government in Baghdad must address the problems of unpaid salaries in the Kurdistan region and to win over the trust of pesh merga fighters.

Although the Iraqi government officially declared victory in its war on the Islamic State last July, peace has not yet been won. Political failures including corruption across government sectors and sectarian divisions, which allowed for the rise of the Islamic State, are yet to be remedied.

Political parties must agree on a framework for governance, especially when it comes to fighting corruption. They must ensure that local security isn’t left to militias and avoid the creation of a vacuum, which will certainly be filled by extremists. Mr. Sadr can meet those challenges with the right allies inside Iraq and abroad.