Going by this list of optionals chosen by Top 100 candidates, it seems Political Science is indeed a good option. I would suggest you refer to last 5 year’s question paper also before making up your mind.
Going by the feedback from my friends who wrote the exam this year with political science as optional, the question paper was very easy this year. Especially Paper I where a lot of direct questions were asked.
If you love the subject and have access to the necessary reading material, by all means select Political Science.