His current term ends today and the new term will be his first full-term lasting three years. Shah's election is virtually a formality, party sources said.
Seen as a close confidante of Prime Minister Narendra Modi, Shah was put at the helm midway during his predecessor Rajnath Singh's tenure after Singh joined the government in May 2014.
Almost all BJP chief ministers, besides a number of union ministers, are likely to be in attendance tomorrow when Shah files his nomination papers and is expected to declared as the party chief.
Under Shah's stewardship, BJP scaled new heights by coming to power in Maharashtra, Haryana, Jharkhand and Jammu and Kashmir but the quite a bit of the sheen was taken off by its massive back-to-back defeats in Delhi and Bihar assembly elections, triggering some rumblings in the party.
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However, party sources have insisted that his "energetic and focused" leadership has strengthened the organisation by pushing its membership across the country and expanding its reach in Assam, Kerala and West Bengal where BJP had never been a force to reckon with.
BJP leader Subramanian Swamy said Jayendra Saraswathi had to undergo imprisonment as he was uniting people.
"Sri Jayendra Saraswahti had to undergo imprisonment. Why ? Because, he was integrating all Hindus and was bringing them in one platform," he said.
"Those who troubled Kanchi Mutt, the law of karma will catch up with them will one day certainly," he said.