RJD supremo Lalu Prasad said his party would support ruling JD(U) to foil the "game" of BJP which had "propped up" two Independent candidates.
Lalu, who has long been a bitter critic of Kumar, the former Bihar chief minister, said his support was based on the need of present times and would comment on the likelihood of his tie-up with Kumar when such a need arose.
"We are told that we should forget the past, should not worry about the future and think about the present. So I am taking this stand on the current agenda (Rajya Sabha election) ... I can't let the BJP's game succeed," he told reporters.
JD(U) has 117 MLAs in the Assembly, including the Speaker, and enjoys support of four Congress MLAs and some Independents but rebellion by a section of legislators following the party's drubbing in Lok Sabha polls has made the victory of its two candidates a bit uncertain.
The support of RJD, which is also plagued by dissidence, may prove to be crucial.
JD(U) President Sharad Yadav has already been elected unopposed to the Upper House but its two other candidates Pawan Verma and Gulam Rasool Baliyawi -- are facing challenge from Independents Anil Sharma, a builder who had contested Lok Sabha election on JD(U) ticket, and Sabir Ali, who had joined BJP but was axed after many party leaders opposed his entry.
BJP has 84 MLAs, RJD 21, Congress four and CPI one legislator while there are five Independents. Since the arithmetic is weighing against ruling JD(U), the support of 21 RJD MLAs is crucial for it in a House of 243, with an effective strength of 232 because of 11 vacancies.