How much can we rely on this survey? How the sampling is done and what is the quantum of sampling and what is the percentage of samples shared between urban, semi-urban and rural areas. Similarly, what is the ratio of educated and uneducated people in the sample? These points will play an important role. You have not mentioned about the survey result completely. Is it the survey done to know only the swing towards these two leaders but not the overall mood of the voter. Did they collect the information about the party that particular people are selecting to vote if not to Kamal or Rajani? In the absence of these details, we can't say it is good for BJP or not. As far as I feel, BJP will have a tie-up with AIADMK and thus it will be benefitted in getting some seats in TN. Otherwise, BJP may not be able to make any seats in the south in the present condition in the Southern part of the country.