India, March 10 -- Now that Nitish Ku mar has quit Bi har's top post, JD (U) faces a challenge to find a replacement for Ni tish, who has a complete command over the party due to his political acu men and also charismatic personality. It won't be easy for JD (U) to fill the void creat ed by Nitish's departure. Another massive chal lenge will be to keep the JD (U) vote bank intact as BJP would try to make inroads into the EBC and caste-neutral women vote banks more aggressively if Nitish does not take extra care to check erosion of his support base, which He created it so meticulously. If JD (U) really loses its electoral capital in the new political scenario, there is a possibility that Bihar politics will become somewhat bipolar - a di r...