Typically, you can only apply to one major, if the school accepts students by major at all. (Many LAC’s ask about majors of interest, but do not admit by major.) Majors like data science and informatics are more likely to be impacted and have barriers to entry if you’re not admitted directly to the major, whereas majors like poli sci are more likely to be accessible. So with these interests, at most schools it will be more important to secure a spot in a data science type major; adding a double-major or minor in poli sci usually won’t be a problem… and if you decide the data science major is more extensive than you need, you can always switch to poli sci after completing the requirements of a DS minor. But switching in the other direction could be difficult, depending on the school. A single program that blends both areas of interest isn’t essential, but can be desirable in terms of advising, having a like-minded cohort, and avoiding having to craft your own interdisciplinary focus.