Lalu Prasad kicked off his "BJP Bhagao, Desh Bachao" rally at Patna's Gandhi Maidan on Sunday.
The rally was attended by West Bengal chief minister Mamata Banerjee.
Akhilesh Yadav of the Samajwadi Party was there too.
As was the Congress's Ghulam Nabi Azad and the CPI's D Raja.
Lalu Prasad's RJD was, till recently, part of the ruling alliance in the state along with the JD(U) and the Congress until Nitish Kumar broke away from the mahagatbandhan (grand alliance) and allied with the BJP.
The JD(U) now rules in Bihar along with the BJP.
The JD(U)'s Sharad Yadav and Ali Anwar also attended the rally.
Sharad Yadav has so far been vocal about his disagreement with Nitish's allying with the BJP.