PATNA, March 6 -- In Bihar, polarisation on caste lines and social affiliations always shape political fortunes of political parties. Bihar chief minister Nitish Kumar, who steered the Janata Dal (United) -- a party he forged and carved into a force -- did it with elan by packaging development politics with deft social enginering. He knit a productive model of herding together exreme backward castes (EBCs), Dalits, Muslims, women and even upper-castes. He yielded dividends of this formula's success in election after elections. Nonetheless, now when CM Kumar is all set to exit from the top post to play a new innings in the central politics, there are indications that the JD(U) strongman's support base among his own caste groups -- they are Kurmis (his won caste), Koeris as Kushwahas, other EB Cs and women may erode a bit and BJP ruling the state from the front, thy might first shift to it. Then, the Opposition RJD may attract these groups towards it in case Kumar's exit sow discontent and despair among these groups. "In past two decades or more, CM Kumar created his own support base by first winning over the EBC caste groups mainly smaller groups in Kosi and north Bihar regions post 2005 as they were not happy with the RJD. Later, Kumar also created a women support group through various schemes be it reservations to women in local bodies, cycle scheme to girl students and also implementing prohibition in 2016. In 2025 elections, Rs.10,000 given to almost 1.56 crore women played a big role in nursing this women support group. This is a new social engineering, which Nitish experimented in last two decades. It worked," said DM Diwakar, a senior political analyst. Poll observers feel that JD(U)'s biggest challenge in coming days once Nitish steps down as chief minister would be to keep the party's support base among Kushwahas -- a formidable OBC group after Yadavs in terms of population -- intact along with the other EBC caste groups. Overall, there are almost 115 EBC caste groups in Bihar and they have a sizeable population of 36% in state's 130 million plus population. "For the NDA constituents, especially the BJP, CM Kumar's exit from the top post would be an opportunity to consolidate its support base among various OBC groups and EBCs which have so far remained loyal to the JD(U). More so, women voters make a formidable support base who have voted for CM Kumar transcending caste lines in last many polls. That would affect the social dynamics of Bihar's caste politics as these groups may splinter in coming years choosing different parties of their choice, if the JD(U) does remain strong," said Rakesh Tiwary, another political analyst and economist. For the RJD , the main Opposition party in Bihar, CM Kumar's own brand of social engineering, especially his image as development-oriented with following among EBCs has remained a big hurdle in expanding its own support base, which mainly constitutes Yadavs, Muslim and a sections of Dalits. Insiders in the RJD said that the party would definitely try to woo the Kushwahas more and also win over the Kurmis....