Guwahati, May 19: Like the blind king Dhritarashtra of the Mahabharat, Assam's Congress chief minister Tarun Gogoi today paid the price for his bias towards his biological heir.

As BJP chief ministerial candidate Sarbananda Sonowal prepares to replace Gogoi, history will record that his party's victory was scripted by Gogoi's one-time blue-eyed boy, Himanta Biswa Sarma.

Biswa Sarma had left the Congress in a huff and joined the BJP last August, rising to become the convener of his new party's election committee within weeks. Today, he brought Gogoi's 15-year rule in Assam to an unceremonious end.

Gogoi's declaration that his son Gaurav, a Lok Sabha member, could not become chief minister came a few months too late. By then, he and his party had been labelled "dynastic".

Biswa Sarma defeated the Congress candidate at Jalukbari in Guwahati by 85,935 votes - 8,532 more than his victory margin over his BJP rival in 2011.

Sonowal won from the river island of Majuli in upper Assam, while Gogoi retained his Titabor seat in upper Assam's Jorhat district.

One of the most high-profile defeats was suffered by Maulana Badruddin Ajmal, self-proclaimed kingmaker, messiah of the minorities and founder of the All India United Democratic Front (AIUDF). Ajmal was vanquished in lower Assam's South Salmara constituency.

While "family politics" may have caused a fatal split in the Congress, these elections were fought on an issue that seems to retain a perennial power to unseat governments - that of illegal Bangladeshi immigrants and the "danger" to the "identity of the Assamese and other indigenous people".

The BJP and its allies exploited the fears to the hilt. The Congress, long accused of helping and protecting the illegal Bangladeshi settlers, once again stands isolated, as it had during the anti-foreigner Assam Agitation of the 1970s and 1980s.

The Asom Gana Parishad (AGP), formed by members of the All Assam Students' Union (Aasu) that led the Assam Agitation, now stands aligned with the BJP. So does the Bodo People's Front (BPF) in lower Assam's Bodo areas, which had turned killing fields in 2012 when minority settlers faced attacks from alleged militants claiming to represent indigenous communities.

Prafulla Mahanta, two-time AGP chief minister and now senior leader of the party, was president of Aasu, as was Sonowal who joined the BJP after a stint in the AGP.

Sonowal's previous big success was as the mover of a public interest petition in the Supreme Court that led to the quashing of the Illegal Migrants (Determination by Tribunals) Act of 1983 in 2005. It was the Congress that had passed the act during the days of Indira Gandhi.

Ajmal had used the abolition of this law to galvanise the minority community in lower Assam and the Barak Valley to set up the AIUDF. Sonowal's success in the apex court had, on the other hand, earned him the popular title of Jatiyo Nayok (national hero).

"We can now finish a job that we had started as members of Aasu," Biswa Sarma had told The Telegraph before the elections.

The BJP's win comes in the face of an appeal from intellectuals not to vote for the "fascist" party.

It is down the corridors of history that this election was fought, inch by inch.

In a largely secular Assam that did not witness riots after the 1947 Partition or the 1992 Babri demolition, this election has added new meaning to the words "Hindu" and "Muslim", turning them virtually into badges slapped onto the chests of voters. In Assam, that would be a first.

Gogoi, 81, accepted the people's mandate with "all humility" but said he would remain in active politics.

"The results obviously make me a little sad but I'm not disheartened. I have seen politics at the national and state levels from close quarters. The defeat of heavyweights implies there was a wave," he told reporters.

"I will definitely remain in active politics. They have promised achchhe din (good days) and I hope they will fulfil the promise."

Insiders say Gogoi enjoys the backing of Sonia Gandhi, something that Rahul Gandhi can't ignore even if he wants to groom a new leader before the 2019 Lok Sabha elections.

Additional reporting by Umanand Jaiswal and Sumir Karmakar