The Bharatiya Janata Party (BJP) has steadily strengthened its electoral performance in Bihar since 2010, while its ally Janata Dal (United) has seen an erosion in vote share and seat conversion.
Data from the last four assembly elections reveals a shifting balance - BJP’s strike rate and vote share have climbed consistently while that of the JD(U) has seen a sharp fall.
BJP Gains, JD(U) Slips
In the 2020 Bihar assembly elections, the BJP won 74 of the 110 seats it contested, achieving an impressive 68 percent strike rate and a 42.6 percent vote share in those constituencies. This marked a sharp rebound from its 2015 performance when BJP won only 34 percent of seats and polled 37.5 percent vote share in contested areas.
JD(U), in contrast, saw a notable slide with the vote share in contested seats dropping to 32.8 percent in 2020 from 40.7 percent in 2015, while strike rate falling to 37.4 percent, barely half of its earlier efficiency.
The trend highlights a shifting balance within the NDA in Bihar, with the BJP emerging as the stronger electoral force even though Nitish Kumar’s JD(U) remains an essential partner in seat arithmetic.
From Dominance to Dependence
The contrast with the past is stark. In 2010, when the BJP-JD(U) alliance was at its peak, JD(U) had won 115 of 141 seats it contested - an 82 percent strike rate - with a 38.8 percent vote share. The BJP, too, delivered one of its best-ever performances, winning 91 of 102 seats at an 89 percent strike rate.
Over the following decade, however, JD(U)’s dominance eroded, and between 2010 and 2020, the strike rate plunged by more than half and vote share slipped by over five percentage points. The BJP, meanwhile, saw its strike rate rise steadily - from 53.9 percent in 2005 to 68 percent in 2020 - reflecting better organisational machinery and vote transfer efficiency across regions.
RJD Retains Core Strength
The Rashtriya Janata Dal (RJD) continues to be the principal opposition force. In 2020, it won 75 seats with a 52 percent strike rate and 39 percent vote share in contested constituencies. Although this was below its 2015 high—when, as part of the Grand Alliance, it had a 79 percent strike rate—the RJD remains the only non-NDA party with consistent statewide reach.
The Congress and Left parties have seen mixed outcomes. Congress’ seat conversion fell sharply from 66 percent in 2015 to 27 percent in 2020, despite a broadly stable vote share.
Smaller Players Struggle
Among smaller formations, the Lok Janshakti Party (LJP) contested the most seats in 2020 (135) but managed to win just one, despite a 10.3 percent vote share in those constituencies. The AIMIM, meanwhile, registered modest but localised gains, winning five of 20 seats it contested.
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