Andhra Pradesh Chief Minister Chandrababu Naidu on Tuesday met Governor Surjeet Singh Barnala and tendered his resignation.
Naidu's Telugu Desam Party, and ally Bharatiya Janata Party, was routed in the assembly election by the Congress-Telangana Rashtra Samithi alliance.
The Congress, which had 91 seats in the dissolved House, is heading for a landslide victory while TDP is being routed even in its strongholds.
Naidu accepted defeat and said his party would play the role of a 'constructive opposition'.
"We accept verdict of the people. We will extend full and wholehearted support to the new government," he told reporters as the election results poured in.
"I thank people of Andhra Pradesh who have blessed me to be in power for the past nine years. I thank my Cabinet colleagues, our alliance partner BJP and the NDA government," Naidu said.
"We will accept the verdict of the people with humility," he said.