Most exit polls have predicted a hung house with the BJP in the lead. If it were to be a hung house, then the Janata Dal(S) would play kingmaker in the state.
Who would the JD(S) support in case it is needed to form the next government in Karnataka?
The question of which party the JD(S) would support in case of a hung house will depend on who is closer to the to the magic number.
In case the BJP seeks the support of the JD(S), then the latter would weigh it on the national scene. If the calculation works to their advantage then the JD(S) patriarch has a chance of making his elder son (Revanna) the Deputy Chief Minister. However the BJP will not concede the Chief Minister's post.
If the Congress is in the lead, then an alliance theoretically seems possible. They are already in an alliance in the BBMP. Moreover, this alliance would also suit the possible national ambitions of the JD(S).
However, there is a big thorn in the flesh and that is the CM (Siddaramaiah). The JD(S) would have the pre-condition that Siddaramaiah is not made the CM. There are also a lot of other Congress leaders who are looking at this possibility.