PATNA/NEW DELHI, March 6 -- Bihar chief minister Nitish Kumar on Thursday announced his candidature for the Rajya Sabha as a Janata Dal (United) nominee, signalling the end of an era in the heartland state just four months after winning a thumping majority in assembly polls along with ally the Bharatiya Janata Party which now looks set to have its first chief minister in one of the country's most electorally important provinces. Kumar, 75, filed his papers for the March 16 Upper House polls flanked by Union home minister Amit Shah, deputy chief ministers Samrat Choudhary and Vijay Kumar Sinha and JD(U) leaders in Patna. The ruling National Democratic Alliance (NDA) commands a brute majority of 202 in the 243-member assembly and is comfortably placed to ensure Kumar's victory. But his unprecedented transition to the Rajya Sabha, months after winning a historic fifth term (he has been sworn in a record 10 times), creates a vacuum in state politics, which has been dominated since 1990 by Kumar and former CM Lalu Prasad. His son Nishant Kumar, who is likely to join, may be accommodated in the state cabinet and may even be elevated to deputy chief minister, said a senior JD(U) leader on condition of anonymity. State parliamentary affairs minister Vijay Kumar Chaudhary said Nishant officially joining the party was a mere formality. "It will happen at the right time," he added. Considered one of India's tallest regional leaders, Kumar has continuously ruled Bihar since 2005 - save a nine-month stint by his former associate Jitan Ram Manjhi - and recently steered the JD(U) to success in the 2024 general elections and 2025 state polls. His successor is likely to be picked from the BJP. Among the frontrunners are Union minister Nityanand Rai and deputy chief minister Samrat Chaudhury, said a BJP leader, requesting anonymity. Kumar expressed gratitude to the people of Bihar for trusting him for over 20 years, saying their support enabled him to serve the state with dedication. "The strength of your faith and support has helped Bihar present a new dimension of development and dignity," Kumar said. He added that he had expressed his gratitude to the people on several occasions earlier. Kumar said that since the beginning of his parliamentary career, he nurtured a desire to become a member of both Houses of Parliament in addition to serving in both Houses of the state legislature. "In that sequence, I wish to become a member of the Rajya Sabha in the election being held this time," he said on X. Kumar reassured people that his relationship with them would remain unchanged despite the move. He said he would continue working with the people to fulfil the goal of building a developed Bihar. Kumar added he would extend full cooperation and guidance to the new government that takes charge in the state. Alongside Kumar, BJP chief Nitin Nabin, Union minister Ram Nath Thakur of the JD(U), Rashtriya Lok Morcha chief Upendra Kushwaha and BJP state general secretary Shivesh Kumar also filed their papers. To win all five Rajya Sabha seats from Bihar, the NDA requires three Opposition lawmakers to cross-vote. Kumar is expected to vacate the chief minister's post only after the nomination process, election, and oath as a member of Parliament are completed. Shah described Kumar's tenure as glorious. "Bihar's CM also filed his nomination for the Rajya Sabha. With this, after a long gap, he will once again enter national politics as a Rajya Sabha MP. Nitish Kumar served as CM of Bihar from 2005 until now. His tenure was truly glorious. This tenure will be written as a golden chapter in Bihar's history, shaping the entire gamut of Bihar's development... Throughout his long career as an MLA, MP, chief minister, and Union minister, his kurta was never stained. His entire life was free from corruption charges," said Shah. Rashtriya Janata Dal leader Tejashwi Yadav called the decision a "betrayal" of the people's mandate. "We have been saying from the very beginning that the BJP will not let Nitish Kumar remain the chief minister after the elections. This is exactly what has happened. This development is against the mandate of the people and amounts to a betrayal of it," he said. To be sure, the BJP is the senior partner in the alliance in the state, with 89 members in the 243-strong assembly, to the JD(U)'s 85. The BJP leadership is expected to balance multiple factors while choosing Kumar's successor. The decision will not only be about seniority but also about caste representation, coalition stability, and the broader political message the party wants to send. Extremely Backward Classes (EBC) and women - two constituencies Kumar has made his own - are likely to figure prominently in the decision-making. Patna-based political observer Kaushalendra Priyadarshi said one possibility could be that the chief minister's post goes to the BJP, and JD(U) continues to hold key government positions, including the deputy chief minister's post. "Such an arrangement would help maintain stability within the alliance at a time when a leadership transition could otherwise trigger uncertainty," he said. He said the Tejashwi Yadav-led Rashtriya Janata Dal (RJD) is likely to attempt to capitalise on any dissatisfaction within the NDA, particularly if the leadership change creates friction among allies Kumar -- who served in both houses of Bihar, four terms in the Lok Sabha, and was a former Union minister of railways, agriculture, and transport in the A B Vajpayee-led NDA government -- is widely credited with transforming Bihar's governance and building a unique appeal cutting across regions, caste, gender and faith. Some of his signature moves - such as prohibition - were controversial but his strategy of fusing welfare with everyday governance, and stitching together a vote base among smaller marginalised castes netted rich rewards. The 2025 Bihar elections turned into a virtual referendum on Kumar's rule with the Opposition's focus on his health and erratic statements. But Sushashan (good governance) Babu's stature cast a tall shadow on others, and a cash handout scheme aimed at women did the rest. Born in Bakhtiyarpur in 1951 to a middle-class family, Kumar was influenced by socialist leader Ram Manohar Lohia and entered the Bihar assembly in 1985. He backed Lalu Prasad as leader of opposition in 1989 and as CM a year later. The two fell out in 1994, and in 1996, he aligned with the BJP. On March 3, 2000, he became chief minister of Bihar for the first time but his term was short-lived-only seven days-as he failed to prove his majority. He became the CM again in 2005 and never looked back. He left the NDA twice: once for four years between 2013 and 2017, and again for two years between 2022 and 2024, allying with the RJD both times, but eventually returned to the fold. Emerging from the socialist churn of the post-Emergency era, Kumar was one of the key actors of Mandal politics He won five consecutive terms in Bihar, swapped partners four times, suffered a drubbing without the BJP in the 2014 general elections and recovered, and emerged as the most indispensable man in the only heartland province that hasn't seen a BJP chief minister at the helm - till now....