Several opposition parties on Thursday decided to field Rashtriya Janata Dal leader Manoj Jha as their joint candidate for the September 14 election of the Rajya Sabha deputy chairman.
Jha will file his nomination papers on Friday in presence of leaders of various opposition parties.
He will contest against National democratic Alliance's nominee Harivansh of the Janata Dal-United.
Harivansh was the RS deputy chairman till his previous term ended.
He has since been re-elected to the Upper house from Bihar.
Jha was teaching in the Delhi University when he entered politics and became a Rajya Sabha member.
He is also the national spokesperson of the Rashtriya Janata Dal.
The RJD and the JD-U are arch-rivals in Bihar where assembly elections will be held very soon and the Rajya Sabha will witness a battle between the two regional parties.
Sources said a number of opposition leaders, including Leader of Opposition in Rajya Sabha Ghulam Nabi Azad, Congress deputy Leader Anand Sharma, Congress's chief whip in RS Jairam Ramesh and others from
Trinamool Conress, Left parties, the Dravida Munnetra Kazhagam, the Aam Aadmi Party and some other parties, will accompany Jha when he files his nomination papers.
The Congress had said it will not let the post of deputy chairman go uncontested and will put up a joint candidate.
Rajya Sabha member M V Shreyams Kumar backed the candidature of Jha, saying his victory is "crucial" for upholding the country's democratic values.
"I offer my support to the candidature of Prof Manoj Jha. His candidature and his victory is crucial for the opposition unity and for upholding the democratic values of our country," M V Shreyams Kumar, who is also leader of Loktantrik Janata Dal, said in a statement.
Harivansh had defeated Congress leader B K Hariprasad last time and won by 125-105 votes in elections held in August 2018.
Since then, the NDA has strengthened its position in the Rajya Sabha further.
Harivansh has already filed his nomination papers on Wednesday.
Bihar chief minister Nitish Kumar on Thursday dialled Odisha's Naveen Patnaik, seeking his party's support for Harivansh, sources said.
Patnaik's Biju Janata Dal had supported Harivansh in the last election.