I agree with your last line. We have numerous parties that are "caste based". Bigger parties typically have alliance with the smaller "caste based" parties because they can win the votes of people who are of particular caste.

One such example of a party(there are many) is

http://en.wikipedia.org/wiki/Pattali_Makkal_Katchi [From wikipedia] >Ramdoss had earlier worked with the Vanniyar Sangham (Vanniyar Union) founded by him in 1980. PMK is based amongst the Most Backward Class Vanniyakula Kshatriyas community.

Vanniyar is a caste in the south Indian state of Tamil Nadu