Datanomics: Incumbents boosted JD(U) and BJP vote share in Bihar

Only 64 constituencies or one-fourth of the total strength of the house had re-elected the same parties in 2010

Over half of the 243 Assembly seats elected the incumbents in the just-concluded Bihar elections. In 2010, this proportion was just one-fourth, as 63 constituencies re-elected incumbents. Notably, both the BJP and JD(U) registered a rise in their vote share in most of the constituencies where they were re-elected this time.

 

Chart 1: Constituencies that voted for same parties up 3x

 

The share of seats sending incumbents to the Assembly rose significantly, from 26 per cent in 2010 to 53 per cent in 2025. The number of constituencies where parties were re-elected and registered an increase in vote share grew over three times compared to the previous Assembly polls — from 32 in 2010 to 101 in 2025.

 

CHART 2: BJP strengthened its base since 2010 polls

 

In 2010, 11 seats on which BJP was re-elected saw an increase in its vote share. In 2025, that number rose to 47.

 

chart 3: Most narrow-win constituencies saw drop in vote share

 

Out of 12 constituencies where parties were re-elected with the lowest margins, 7 recorded a decline in vote share between 2020 and 2025.