MUMBAI, Jan. 20 -- India's ruling Bharatiya Janata Party (BJP) on Tuesday elected Nitin Nabin, 45, as its youngest-ever party president, signaling a generational shift aimed at winning over the country's young electorate.

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Nabin, a five-time legislator from Bihar-India's poorest state-was elected unopposed as the BJP's 12th president, succeeding JP Nadda, 65, just months ahead of critical state elections, including in West Bengal, a region the party has yet to secure.

Hundreds of party workers gathered at BJP headquarters in New Delhi as Nabin, with a vermillion mark on his forehead and shoulders draped in a scarf bearing the party symbol, took the oath of office before Prime Minister N...