Former BJP minister B Sriramulu, who had been dropped from the cabinet after BS Yeddyurappa resigned as Karnataka chief minister, has quit the party.
On Wednesday he submitted his nomination for byelection in Bellary (Rural) as an independent candidate.
Sriramulu is a close aide of former minister and mining baron B Janardhana Reddy, now in jail on charges of illegal mining, and helped the BJP to win power for the first time in a south Indian state in 2008.
"I have not betrayed the party. I had worked for the party and gave strength to it. But the party sidelined me, forcing me to seek re-election as an independent," Sriramulu said after filing his nomination papers.
The bypoll is on November 30.
Sriramulu, a scheduled tribe leader, is claiming he has the support of 15 MLAs in the assembly, which now has 225 members, including the Speaker. The sanctioned strength is 226.
The BJP and allies have 118 members.
To stress his closeness to the party central leadership, Sriramulu once referred to BJP leader Sushma Swaraj, who lost to Congress president Sonia Gandhi from the Bellary Lok Sabha seat in 1999, as 'Amma'.
In a letter to BJP chief Nitin Gadkari, Sriramulu has said the state unit of the party sidelined him, and some leaders were trying to "finish him" politically. This was despite the "help" the state BJP received from Sriramulu and the Reddy brothers (Janardhana and former minister Karunakara Reddy) during every crisis, he said.
Before filing his nomination, he met Janardhana Reddy at Chanchalguda prison in Hyderabad. MLA Somashekhar Reddy, who is also Janardhana Reddy's brother, was with him at the time of filing his nomination.