The BJP's southern fort where it came to power for the first time in 2008 crumbled and the party may be pushed to the third position behind JD(S).
Exploiting the split in BJP and the spoiler's role played by former Chief Minister B S Yeddyurappa, the Congress was ahead in 93 of the 223 constituencies that went to polls and has already won 11 seats.
The JD(S) led by H D Deve Gowda won two seats and was ahead in 39 seats while the BJP bagged one and is leading in 35 seats.
The fledgling Karnataka Janata Party (KJP) floated by Yeddyurappa after his exit from BJP was leading only in more than ten seats while independents and others were ahead in 15 seats.
In the elections five years ago when BJP stormed to power for the first time in a southern state on its own, the party had won 110 seats against Congress' 80 and BJP's 28.
In the 224-member house, 113 seats would be required for majority. Polling was held in 223 segments, with the one in Periyapatna in Mysore district put off to May 28 following death of BJP candidate.
Significantly, KJP has damaged the prospects of the BJP in many constituencies, eating into its votes.
The Congress appeared set to for a clean sweep in the coastal Dakshina Kannada district, a traditional BJP stronghold.
But it was the JDS of former Prime Minister H D Deve Gowda which was the surprise package of the polls, faring better than expected.
In Bangalore urban areas, which has a total of 28 seats, the Congress was ahead in 11 and the BJP in eight.