Why even 70 seats is too much. They can be reduced to single digits.
The CNN-IBN survey has showed that the BJP lacks a pan Karnataka character. It is mainly supported by Lingayats concentrated in the Mumbai-Karnataka region (50 seats)where it is poised to sweep. In all other regions, BJP is wiped out or trailing a distant second.
So two steps is all that is required to reduce BJP to single digits:
1. Informal election understanding among secular parties like they did in the case of Yediruppa - JD(S) not fielding a candidate and Congress fielding a very weak candidate - the combined impact consolidates the anti-BJP votes. This has happened already.
2. Tactical voting by non-Lingayats against BJP to counter the Lingayat consolidation behind BJP
This way, the Congress wins and the JD(S) becomes the main opposition party - the good old days of decent politics without riots!