The problem with Rajnikanth as I see it is that he is a reluctant politician. His large fan base pushes him to make political statements, but then when opposed he fails to make political capital out of it.
This sticks him right in the middle of the devil and the deep sea.
His recent comments on the Cauvery issue angered the Kannadiga's so much so in order for 'Kuselan' to have a safe run in Karnataka he had to tender an apology, which in turn diminished him before his fans in Tamil Nadu.
What he should have done instead is to go the whole hog and make political capital out his comments. He could have used the Kannadiga's anger to fuel his popularity in Tamil Nadu by refusing to apologize. Sadly, he baulked.