The surrender of dacoit Phoolan Devi in 1983 was a significant event during his tenure as Chief Minister of Madhya Pradesh, reflecting efforts by his government to restore law and order, particularly in the Chambal region, while also dealing with the underlying socio-economic issues.

In 1980, when INC achieved a simple majority in the assembly, he won from Churhat and became the Chief Minister of Madhya Pradesh, despite the presence of strong contenders such as Sethi, Vidya Charan Shukla and Shiv Bhanu Singh Solanki.

[6] As chief minister, Singh implemented several populist initiatives, including the regularisation of slums and providing free electricity connections to residents.

[7] He led the INC to victory in 1985, yet again winning from Churhat, but was forced to resign as Chief Minister after just one day due to differences with Sriniwas Tiwari.

He was elected to the Lok Sabha from South Delhi in a bypoll in 1985, necessitated by the assassination of the sitting MP Lalit Maken.

The Ninety-third Constitutional Amendment, that was introduced by the First Manmohan Singh ministry, granted a 27% reservation for Other Backward Classes in all Central Government educational institutions.

Later on, students took legal action against the Act by filing Public Interest Litigation, claiming that it violated the Basic Structure of the Constitution of India.

[8] In April 2008, a 5-member constitutional bench of the Supreme Court, in the Ashoka Kumar Thakur v. Union of India case, upheld the Ninety-third Constitutional Amendment, and reinstated the Act in a judgement delivered by Chief Justice India K. G. Balakrishnan, with Justices Arijit Pasayat, C K Thakker, R V Raveendran and Dalveer Bhandari.

[9] Arjun Singh was the Chief Minister of Madhya Pradesh when the deadly gas leak from the Union Carbide factory occurred.

[11] In particular, the pilot of the aircraft in which Warren Anderson flew out of India after the gas leak, has recorded that the final sanction to permit the flight came from Arjun Singh's office.

The Churhat Children Welfare Society was floated in 1982 by relatives of Singh, and permitted to raise funds via lottery, and also given tax relief as a charity.

[13] However, there were widespread allegations[14] that substantial sums of money were siphoned off from donations and used to construct the lavish Kerwa Dam Palace near Bhopal.

At a public litigation hearing, the Madhya Pradesh High Court observed that "Arjun Singh owed an explanation to the nation about the costs and sources of construction of the palatial mansion in Bhopal".

In court, the case was argued by Kapil Sibal and the order for re-examination was squashed on the grounds that it had been issued in a haste and "had not applied his mind".

This followed his denouncement of the Ekal Vidyalayas, one-teacher schools run for the benefit of the tribals of India by the Vishwa Hindu Parishad,[18] as communal.

He had been admitted in Delhi's All India Institute of Medical Sciences with chest pain and neurological problems, and died of a heart attack.