President Ram Nath Kovind, Vice President M Venkaiah Naidu, Prime Minister Narendra Modi and other leaders condoled the death of Veerendra Kumar.
JD-U Rajya Sabha MPs Ali Anwar and M P Veerendra Kumar met senior leader Sharad Yadav amid reports that he was also displeased with Nitish Kumar's action.
Moves are being made by senior leaders of Janata Dal (Secular) for his expulsion from the party.
A day after he defied the party whip and voted in favour of the United Progressive Alliance government's confidence motion, Janata Dal-Secular MP Shivanna was on Wednesday expelled from the party. JD-S secretary general Danish Ali told PTI that steps have been initiated to disqualify him from the Lok Sabha and a letter was being sent to the speaker in this regard.
Unsubstantiated and illogical opinions, delivered freely from within or abroad, could not destroy the democratic nature of the country, he added.
The members, whose terms are ending, include union ministers Ravi Shankar Prasad, Dharmendra Pradhan, J P Nadda, Thaawarchand Gehlot and Ramdas Athawale.
Janata Dal-United chief Sharad Yadav on Wednesday shared the dais with Samajwadi Party supremo Mulayam Singh Yadav on the inaugural day of SP's national convention in Lucknow, fuelling speculation about their joining hands.
Congress president Sonia Gandhi has convened a meeting of the party's strategy group on September 8, the sources said. Opposition leaders are keen that various like-minded parties should work closely with each other to take on the government in Parliament.
The saffron party is assured of victory in eight of the ten seats in UP going by its dominant numbers in the state assembly.
Biennial elections are being held for 58 Rajya Sabha seats across several states and by-poll for one in Kerala.
Mayawati was outmanoeuvred by the BJP in the race for the Rajya Sabha in Uttar Pradesh just days after she helped the Samajwadi Party snatch two Lok Sbaha seats from the saffron party in bypolls.