The Enforcement Directorate (ED) arrested Singh, 51, on Wednesday in connection with the agency’s investigation into alleged irregularities in the implementation of Delhi excise policy.

Singh has been at the forefront of the party’s efforts at both attack and defence. “Whenever AAP faced a crisis, such as during the arrest of Manish Sisodia and Satyendar Jain or when the Centre promulgated an ordinance to nullify the Supreme Court’s order giving control of Delhi’s bureaucracy to the Arvind Kejriwal government, Sanjay Singh strongly defended the party -- from streets to the Parliament,” said a party leader who asked not to be named.

Singh was born in a middle-class family in Uttar Pradesh’s Sultanpur in 1972. His parents were government teachers. He went on to do a diploma in mining engineering from Orissa School of Mining Engineering, Keonjhar in 1993 but seemed to find his calling when he founded the Azad Samaj Seva Samiti in Lucknow in 1994 and started working for the betterment of miners and street hawkers.

Singh joined hands with Kejriwal’s right to information campaign in 2006 and was part of the 2011 anti-corruption movement which eventually morphed into the AAP. Currently, Singh is a member of the party’s apex decision-making body, the Political Affairs Committee which takes all important decisions. He was also in charge of the state unit of the party during the Punjab assembly elections in February 2017 and spearheaded AAP’s civic body polls campaign in Uttar Pradesh in 2017.

Singh was elected to the Rajya Sabha in 2018 ; he has raised over 200 starred questions in Parliament and introduced three private member bills. He is one of the AAP’s national spokespersons and now in charge of the party’s efforts in Uttar Pradesh, Odisha and Rajasthan. Last month, Singh was appointed as a member of INDIA’s campaign committee. He has been among the three top leaders from the AAP at INDIA meetings (the others have been Kejriwal and MP Raghav Chadha). In most meetings of opposition parties, Singh is usually present and the most vocal.

“After the arrest of Manish Sisodia, Singh was playing a larger role in the party and was working closely with Kejriwal in the formation of INDIA bloc. Even within the party Singh is a crowd puller because he is accommodating and listens to everyone,” said an AAP leader who asked not to be named.

Sanjay Kumar, political analyst and professor at Centre for the Study of Developing Societies, said the back-to-back arrests of AAP leaders will affect the public perception of the party besides taking a toll on the morale of the party workers. “In politics it is common for politicians to face cases, but the back-to-back arrests of leaders in alleged corruption cases and the denial of bail for a long time will hit the public perception. It may cause a large section of people to think that because the AAP leaders are not getting bail, there must be something fishy. The arrested leaders are not small leaders, they are prominent faces of the party,” said Kumar. He added that the arrests were unlikely to have a major impact in the next round of state elections -- because the AAP isn’t a major player in any of the states going to polls.

Tanvir Aeijaz, associate professor of political science at Ramjas College, said Singh formed the backbone of the AAP when it came to attacking the party’s political opponents. “Such leaders help to perpetuate a particular perception against their political opponents. But the arrest of bold leaders creates a bigger impact. The arrest of Sanjay Singh regardless of the merits of the case will have a spillover effect .”