The first phase will see voting in 47 constituencies which mainly constitute the eastern part of Bihar. The districts of Bihar that will go to polls in the first phase are Madhubani, Supaul, Araria, Kishanganj, Purnia, Katihar District, Madhepura and Saharsa.
Congress and BSP are contesting on all 47 seats. JD(U) is contesting 26 seats while its ally BJP is on the other 21. NCP is fighting alone on 33 seats. RJD is on 31 with friendly fight with LJP on several seats. LJP itself is contesting on 26 seats. The Communist parties are fighting on some seats with CPI-M on 7, CPI on 17 and CPI-ML on 11. The first phase seats are mainly considered a NDA stronghold. In the Lok sabha elections of 2009, JD(U)+BJP won 34 seats here out of a total of 47.
You can find more details on Bihar Phase 1 polls here.