RCP Singh, a close confidant of Bihar chief minister Nitish Kumar, was on Sunday chosen as the new president of Janata Dal-United.
Kumar had proposed the name of Singh for the top post, which was then approved by other members during the party's national executive meeting.
The chief minister, who was re-elected as the JD-U president in 2019 for three years, relinquished the post in favour of Singh, its leader in Rajya Sabha.
Singh, a bureaucrat-turned-politician, was so far the general secretary of the regional party.
The JD-U is holding its national executive meeting to deliberate on issues related to the country's political situation, after six out of the party's seven MLAs switched over to the BJP.
Polls in neighbouring West Bengal also came up for discussion at the meeting, the senior leader said.
Singh who prefers to keep a low profile was so far the general secretary (organisation) of the regional party.
The 1984 batch IAS officer of Uttar Pradesh cadre has been with Kumar since his stint as the Railway minister in the government led by late Atal Bihari Vajpayee.
When Kumar returned to the Bihar politics becoming chief minister in November 2005, Singh too came to his native state and became Principal Secretary to the CM.
Months before retirement from service, he quit the job and joined politics in 2010.
Kumar soon made him a member of the Rajya Sabha and he continues to be part of the Upper House of Parliament.
A man of a few words, Singh loves to stay in the shadow of his master (Kumar) with whom he shares not only the Kurmi caste affiliation but also close personal bondage.
With the JD-U passing through hard times losing its "elder brother" status to the BJP in the NDA in Bihar after not faring well in the recently concluded assembly election, the task is cut out for the 62-year-old Singh to strengthen the organisation as well as deal astutely with the saffron party.
The JD-U could win only 43 seats in the Bihar polls, down from 71 in the last elections held in 2015.
The BJP, on the other hand, bagged 74 seats to help the NDA retain power in the state.
The saffron party kept its promise of making Kumar a chief minister irrespective of numbers scored by the partner parties, but Kumar lost the sheen which he enjoyed in the ruling coalition since the Vajpayee-LK Advani era.
The exodus of six of the seven JD-U MLAs in Arunachal Pradesh to the BJP and the upcoming polls in neighbouring West Bengal are immediate challenges for the new JD-U president.
Polls in West Bengal, which is due in April-May next year, also came up for discussion at the national executive meeting.
Born on July 6, 1958, at Mustafapur in Nalanda district, Singh did his schooling from a School at Hussainpur in the same district.
He graduated with a Bachelor of Arts degree in History from Patna College and did Master of Arts from Jawaharlal Nehru University.
Singh married Girija Singh on 21 May 1982, and they have two daughters.
One of his daughters, Lipi Singh, is a 2016 batch IPS officer.
She had hit the national headlines when the police opened fire on a group of people going for immersion of goddess Durga idol in Munger district in October.
In the face of raging protests over the event, she was removed as the district SP on the order of the Election Commission.