Bihar Elections 2025: In the Bihar Assembly Elections 2025, the National Democratic Alliance (NDA) won over 200 of the 243 seats, demonstrating not only electoral dominance but also how India’s first-past-the-post system can amplify vote share advantages when party systems unite around two main alliances.
The math provides an interesting narrative. The Mahagathbandhan (MGB) received 37.3% of the vote, compared to the NDA’s 47.2%, a difference of about ten percentage points. Although noteworthy, this gap is insufficient to account for the NDA’s enormous number of seats. Over the past ten years, Bihar’s party system has undergone a structural upheaval that holds the key to the solution.
The tale of vote consolidation
A strange stagnation may be seen in the MGB’s performance. The coalition was unable to increase its 2020 vote percentage of 37.23% despite adding minor parties including the Indian Inclusive Party, which targeted the Tanti-Paan community (among the Extremely Backward Classes), and the Vikassheel Insaan Party (VIP), which targeted the Mallah community. The caste-based mobilization’s promised math did not result in more votes.
The NDA, on the other hand, had an incredible upsurge, growing its vote share by about ten percentage points. The return of the Lok Janshakti Party (Ram Vilas) to the NDA, which received 5.5% of the vote on its own, was a major factor in this. Furthermore, the BJP and Janata Dal (United) increased their respective vote shares by 1.5 and 3 percentage points.
The gains of the JD(U) deserve special consideration
Transferable votes from LJP (RV) supporters, who in 2020 had only fielded candidates against JD(U) nominees under Chirag Paswan’s leadership, and an increase in female voters, many of whom supported the party due to its welfare programs aimed at women, were two reinforcing factors that helped the party.
Fromย disintegrationย toย bipolarity Historically,ย Bihar’sย politicalย sceneย hasย beenย markedย byย fragmentation,ย withย numerousย partiesย engagedย inย fierceย competitionย acrossย constituencies.
Theย averageย Effectiveย Numberย ofย Partiesย (ENOP)ย duringย Assemblyย andย Lokย Sabhaย electionsย upย tillย 2015ย showsย consistentlyย highย fragmentation,ย withย ENOPย valuesย moreย thanย 3. Becauseย votesย wereย distributedย amongย severalย candidates,ย thisย resultedย inย anย inefficientย conversionย ofย voteย sharesย intoย seatย shares.
By weighing the major political parties in a constituency according to their relative strength, the effective number of parties is an index. Compared to just listing all parties, this computationโwhich was created by Laakso and Taageperaโoffers a more realistic view of the political environment. The final figure aids in determining the level of political division in each seat.
A bipolar contest, for example, is suggested by an index value of 2, a triangular competition by a value of 3, and a fragmented system by a value of 4 or above. On the other hand, a number of 1 indicates that there was just one successful competitor.
The 2019 Lok Sabha elections marked a significant change as the political forces in Bihar were consolidated into two main alliances, the NDA and the MGB, which significantly decreased fragmentation. A bipolar contest began to form when the ENOP fell to 2.58.
The ENOP rose to 3.34 in the 2020 Assembly elections, seemingly reversing this trend, however this was an anomaly brought on by the LJP’s choice to run independently against JD(U) candidates. The political power of unified alliances was shown in the Lok Sabha elections of 2024. The ENOP dropped to 2.41 when LJP (RV) rejoined the NDA and faced the same alliance structure that would last until 2025. As a result of this consolidation, the NDA was able to dominate Assembly divisions throughout the state.
This bipolar structure persisted in the 2025 Assembly elections, but the introduction of Prashant Kishor’s Jan Suraaj Party (JSP) caused a minor increase in fragmentation (ENOP of 2.65). However, it seems that JSP has mostly attracted votes from the anti-incumbency pool rather than challenging the NDA.
The effect of spoilers
The final result was significantly shaped by the JSP’s performance. Together with the All India Majlis-e-Ittehadul Muslimeen, the party split the anti-incumbency vote with 3.5% of the vote. The MGB’s vote share decreased from 40.1% in the 2024 Lok Sabha elections to 37.3% in 2025, a decrease of 2.8 percentage points that was almost identical to the JSP’s.
Such vote divisions may have limited effects in a fragmented party system. However, even little variations in vote share result in disproportionate seat gains for the top alliance in a bipolar campaign that follows first-past-the-post procedures.
Also Read: What next for Congress post Bihar Elections 2025 debacle?
The electoral translation process
Once more, in bipolar elections, India’s electoral system favors concentrated vote shares. The leading alliance frequently sweeps constituencies rather than just gaining more seats when there are only two significant options in the party system. The NDA’s victory in the Bihar Elections 2025 was made possible by its 10-percentage-point advantage in a political climate where the ENOP has dropped below 3.
The combination of alliance consolidation, which concentrated anti-establishment votes within the MGB, and the deliberate fragmentation of that opposition vote by the JSP and AIMIM, which prevented the MGB from fully capitalizing on anti-incumbency sentiment, is the basic math that led to the NDA’s victory in the Bihar Assembly Election 2025.
The BJP has strengthened its position among the higher castes, while the NDA has formed a more varied alliance based on caste identities. In addition to focusing on women as a group, the JD(U) combined support from EBCs, non-Yadav OBCs, and “Mahadalits.”
While lesser parties drew support from the Dalit and Koeri populations, the LJP (RV) catered to the Pasi and other Dalit communities. This could not be overcome by the MGB’s counter-mobilization, which included the Yadav-Muslim base of the RJD and the eclectic support of the Congress and the Left.
