Mohiuddinnagar, located in Samastipur district, is one of Bihar’s 243 Assembly constituencies and falls under the Ujiarpur Lok Sabha seat. The constituency covers around 305 sq km and includes the Mohiuddinnagar and Mohanpur blocks, along with 9 gram panchayats from the Patori block. It shares boundaries with Morwa, Sarairanjan, Mahnar, Bachhwara, Mokama, Barh and Bakhtiarpur.

In the 2020 Assembly elections, BJP’s Rajesh Kumar Singh won the seat with 70,385 votes, defeating RJD’s Ejya Yadav by 15,114 votes. The constituency had 264,479 registered voters that year, with a turnout of 56.03%. According to the 2024 rolls, the electorate has risen to 268,014 (141,185 male, 126,826 female and three third-gender electors). Voting in Mohiuddinnagar will take place in the first phase on 6 November 2025.

Mohiuddinnagar sits in the Mithila region and is named after the Sufi saint Shah Afaq Mohiuddin; the fort Amina Bibi ka Quila still stands as a reminder of that heritage. Despite the name, the Muslim share of the electorate is relatively small. The constituency functions as an important market centre for nearby villages and is characterised by agriculture-driven livelihoods.

Politically, Mohiuddinnagar is known less for ideological loyalty and more for its acceptance of turncoats. Voters here have repeatedly rewarded leaders who switch parties, as seen in the careers of Kapildeo Narain Singh, Ram Chandra Rai and Ajay Kumar Bulganin. The seat has changed hands frequently — Congress has won five times, RJD four, BJP twice, and several other parties have made occasional gains since the constituency was established in 1951.

The BJP currently holds a slight edge heading into 2025. In the 2024 Lok Sabha election, BJP’s Ujiarpur candidate maintained a lead of 6,073 votes in this segment, though this was a sharp drop from the 43,687-vote lead in 2019. With Mohiuddinnagar’s voters historically unpredictable and turnout hovering near 56%, both NDA and RJD will focus heavily on mobilising abstaining voters — a shift of even 5% could flip the result.