The projection in a TV channel and weekly magazine pre-poll survey also says ruling BJP is likely to lose substantial ground in the next month's Assembly polls.
The survey says Congress is set to get around 117-129 seats in the Assembly this time. The party's strength at present is 71.
The BJP, which has 104 seats in the 2008 polls, may get only 39-49 seats in the upcoming elections succumbing to a strong anti-incumbency factor, the survey says.
It says former Prime Minister HD Deve Gowda's JD-S is likely to get 34-44 seats and former BJP strongman BS Yeddyurappa's Karnataka Janata Party (KJP) and Independents together may end up with only 14-22 seats.
The survey shows that Congress is likely to secure 37 per cent vote-share, a two per cent gain compared to its 2008 performance.
The poll suggests a significant fall in BJP's vote share compared to its performance in the last Assembly election. The BJP is likely to get only 23 per cent votes, 11 per cent fall compared to 2008.
It says the BJP's loss is the gain for new entrant and former Chief Minister B S Yeddyurappa's KJP. In its political debut, KJP is likely to get an estimated 7 per cent votes. The JD-S may finish third but with a marginal gain in its vote share, the survey says.
JD-S president and former Chief Minister H D Kumaraswamy is the most preferred Chief Minister candidate with 18 per cent people likely to vote in favour of him, it says.