Guwahati/New Delhi: Assam was waiting for him ever since he won a major legal victory over illegal immigrants in 2005. And for the next five years, Sarbananda Sonowal will script the state's history, thanks to the mandate handed to him by the people in the assembly polls. The indications were clear ahead of the assembly elections -- and that's exactly what happened: the 53-year-old Bharatiya Janata Party (BJP) leader is now poised to lead Assam as its new chief minister. Born in the tea district of Dibrugarh in 1962, Sonowal was a student leader in his younger days. He was a member of the All-Assam Students Union (AASU) and served as its president between 1992 and 1999. He later entered active politics by joining the Asom Gana Parishad (AGP). Sonowal shot to fame in 2005 when he took up the issue of "illegal infiltration from Bangladesh" and moved the Supreme Court for removing the Illegal Migrants (Determination by Tribunal) Act, 1983. In its landmark judgment on July 12, 2005, the apex court struck down the act as being "unconstitutional" and termed Bangladeshi infiltration an act of "external aggression". The judgment has had its impact on Sonowal's political career: he became the 'Jatiya Nayak' (National Hero) of Assam, a title bestowed on him by the AASU. However, Sonowal was aiming to spread his wings beyond a regional outfit. In 2011, he left the AGP and joined the BJP. The same year, he was appointed to the party's national executive and made the spokesperson and general secretary of the BJP's Assam unit. In 2012, Sonowal was appointed president of the state BJP -- and there was no looking back since then. While much of the credit goes to Sonowal for BJP's historic victory in Assam, it is also the 'tribal' factor which catapulted the saffron party to power in this northeastern state. In fact, Sonowal's selection as the chief ministerial candidate was a well-thought-out strategy. BJP, which is perceived as a 'north Indian' party, was able to cobble up support of the tribals --- Moran, Muttock, Tai Ahom, Koch Rajbongshi, Sootea and the tea tribes, besides the Kachari tribe to which Sonowal belongs. These tribals from the plains have a significant presence in upper Assam districts of Jorhat, Golaghat, Sivsagar, Dibrugarh, Tinsukia, Lakhimpur and Dhemaji. "BJP was always an accepted political force for upper caste Hindu Assamese, but Sonowal and a few others, like tea tribe leader Kamakhya Tassa, gave BJP new foothold. The election results in Assam exemplify that paradigm shift and hopefully it's a new beginning under Sonowal," Guwahati-based political analyst Ratnadeep Gupta told IANS. The alliance BJP worked out with tribal group Bodo People's Front (BPF) also helped the party-led National Democratic Alliance (NDA). Observers feel the basic credit should go to the strategy team which advised the BJP leadership to project Sonowal as the chief ministerial candidate and work out an alliance with the Bodo People's Front (BPF). In the last assembly election, the BPF was in alliance with the Congress. Till end of November 2015, BJP was not sure about the tie-up with the BPF. But Ram Lal, BJP's organisational general secretary, had said that only such a tie-up will put the BJP on track in Assam. His calculation seems to have worked out pretty well. This alliance did well across the Bodoland Territorial Area Districts (BTAD) comprising Kokrajhar, Kajolgaon, Udalguri and Baksa districts. The BJP calculation that Bodos can influence results in as many as 25-30 assembly seats in the state has brought in dividends. Significantly, at a later stage the Bodos had decided to extend support to the Gorkhas, Kalitas, Koch-Rajbongshis and Adivasis for ST status. To Sonowal's credit, he synthesised his tribal identity with his brand of Hindutva politics. His staunch opposition to the Bangaldeshi migrants suited both the Rashtriya Swayamsevak Sangh (RSS) and BJP in their quest for power beyond river Brahmaputra in the northeast. And as we see now, it did wonders for the saffron outfit which had just six MLAs in the previous assembly. Sonowal has delivered the state to his leader Narendra Modi. This despite the fact that the 'Modi wave' of 2014 was either on the wane or didn't exist. Delighted by the success, 53-year-old Sonowal attributed it to the "family-like team work" of BJP leaders, including Prime Minister Modi, BJP chief Amit Shah and a new entrant Himanta Biswa Sarma.