With the Congress announcing a second candidate, contest is likely for nine seats of Maharashtra Legislative Council for which Chief Minister Uddhav Thackeray is among those in the fray.
Contest will become inevitable if no candidate withdrew nomination by May 14.
As the Congress had earlier decided to field only one candidate for the May 21 election, there were nine candidates in the fray for as many seats.
But on Saturday evening, state Congress chief Balasaheb Thorat tweeted that Rajkishore alias Papa Modi will be party's second candidate besides Rajesh Rathod, Jalna zilla parishad member whose name was announced from Delhi. He was confident that both will win, Thorat added. Modi is the party's Beed district unit chief.
The 288-member Maharashtra Assembly forms electoral college for the polls, and a candidate needs 29 votes to win.
The Congress has 44 MLAs.
The last day of filing nomination is May 11, scrutiny of nominations will take place on May 12 and the last date of withdrawal of papers is May 14. The nine seats fell vacant on April 24 after terms of the sitting MLCs ended.
The Shiv Sena and NCP, other two ruling alliance partners, have so far announced two candidates each, while the opposition BJP has announced four candidates.
Mr Thackeray, who is not a member of either Houses of the state legislature, and incumbent deputy Chairperson of the Legislative Council Neelam Gorhe are the nominees of the Sena while Shashikant Shinde and Amol Mitkari are the candidates of the NCP.
Former NCP MP Ranjitsinh Mohite Patil, Gopichand Padalkar, Praveen Datke and Ajit Gopchhade are the nominees of the BJP, which has the highest 105 MLAs.
The BJP nominees filed their nominations on Friday. Mr Thackeray will be filing his papers on May 11.