Kishor is on course to defeat BJP candidate Neeraj Kumar Sinha by nearly 20,000 votes, while RJD's Rekha Gupta has slipped to third place.
For Jan Suraaj, the victory is a major breakthrough.
After contesting all 243 seats in the 2025 Bihar Assembly elections without winning a single constituency, the Bankipur win gives Kishor the political momentum he has been seeking to establish himself as a serious force in the state.
While the immediate setback is for the BJP, the longer-term political implications may be more serious for Tejashwi Yadav and the RJD.
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Why Tejashwi has more to worry about
The BJP has lost one of its safest urban seats, but it remains the dominant force in Bihar after its sweeping performance in the 2025 Assembly elections.
For the BJP, Bankipur is a symbolic setback rather than an existential one.
For the RJD, however, Kishor's emergence creates a new challenge. In the bypoll, the party has been pushed to third place despite finishing second in the 2025 Assembly election.
In that election, the BJP secured nearly 63 per cent of the vote in Bankipur, while the RJD polled 29.55 per cent. The bypoll suggests that Kishor is beginning to occupy the political space that the RJD has traditionally claimed as the principal challenger to the NDA.
If Jan Suraaj continues to grow, it could attract anti-BJP voters who increasingly see Kishor - not the RJD - as the candidate best placed to challenge the NDA.
A longer wait for power?
That possibility matters because the RJD has been trying to return to power for nearly two decades.
The RJD's 15-year rule ended after the February 2005 Assembly election produced a hung verdict, followed by President's Rule. In the November 2005 election, the JD(U)-BJP alliance led by Nitish Kumar formed the government, ending the RJD's uninterrupted stint in power.
Since then, the RJD has not headed a government in Bihar. It briefly returned to office as part of the Mahagathbandhan government between August 2022 and January 2024. Tejashwi Yadav served as Deputy Chief Minister after Nitish Kumar switched sides. However, the Chief Minister's post remained with Nitish.
Tejashwi came closest to power in the 2020 Assembly election, when the RJD-led Mahagathbandhan won 110 seats- just 12 short of the majority mark. The NDA secured 125 seats.
In 2025, the BJP-led NDA swept back to power with 202 seats, reducing the Mahagathbandhan to just 35. The RJD's tally fell from 75 seats in 2020 to 25, while the BJP emerged as the single-largest party with 89 seats, followed by the JD(U) with 85.
Against that backdrop, Kishor's rise could complicate the opposition's path even further.
If Jan Suraaj succeeds in consolidating anti-NDA votes without defeating the ruling alliance across the state, it risks dividing the opposition space and making Tejashwi Yadav's wait for the Chief Minister's office even longer.