Your query indicates clearly you are influenced by Tina Dabi’s success in CSE 2015 and wish to emulate her success.
Some of my friends in Delhi University confirmed that there is a craze about Political Science this year.
I recommend, you should always go with your aptitude and if you feel comfortable with science subjects that should be your first priority.
You should think twice before taking such a big decision.
Civil Services Examination has vast syllabus and maximum weightage is for General Studies. As far as optional subject is concerned, candidates with different optional subjects crack this examination.
By chance, you are willing to change the stream just for sack of usefulness of a particular subject with respect to Civil Services Examination, I have an opinion that Political Science is one of the most suitable subjects that renders help in Civil Services Examination preparation.
It is difficult to predict what kind of changes we witness in Civil Services Exam-plan by the time you become eligible to appear; but, whatever happens, I feel Political Science background will prove to be helpful.
Philosophy is also a very good subject and results are good; but, you should consider its utility in addition to option in Civil Services, what else it offers…
But, before saying yes, you should consider that this subject (Political Science) is of your liking or not and will you be able to perform with it…