The correct answer for this question is option 2, Rajni Kothari.

Option 1, D.L. Seth, is not the correct answer.

Option 3, James Manor, is not the correct answer.

Option 4, Christophe Jaffrelot, is not the correct answer.

The term "Congress System" refers to a period in Indian politics where the Indian National Congress party dominated the political landscape. It was coined by Rajni Kothari, a renowned Indian political scientist and scholar. Kothari used this term to describe the hegemony of the Congress party in the post-independence period, where it played a dominant role in shaping and governing India`s political system.

It is important to note that while the provided answer is generally correct, there might be alternative perspectives or scholars who have also made significant contributions in studying and defining the Congress System. However, for the purpose of this question, Rajni Kothari is considered the most commonly associated scholar with the term.