It dropped sitting MP from Guna, Krishnapal Singh Yadav, to field Union Minister Jyotiraditya Scindia from the seat.
The highest percentage was reported from constituencies in Karimganj, Jorhat and Haflong districts ranging from between 35 to 40 per cent.
The defeat of their leaders has stunned party workers of the Asom Gana Parishad and the Bharatiya Janata Party to silence.
The BJP-led alliance in Assam is all set to form the government for the second successive term winning 72 of the 102 seats declared so far and is leading in three others.
As per the plans, the survey will be conducted to identify people of four communities -- Goria, Moria, Desi and Jolah of the tea tribes -- considered as indigenous.
Himanta Biswa Sarma -- who is also the North East Democratic Alliance convenor -- took the oath of office and secrecy in Assamese.
Sarbananda Sonowal was on Tuesday sworn in as the 14th chief minister of Assam in the presence of Prime Minister Narendra Modi, Bharatiya Janata Party president Amit Shah and other dignitaries at a huge public function at Khanapara field.