Poltitcal Science major at target school looking to enter IB

I am a rising sophomore at a target school near Charlotte and would like to start a career in investment banking after college. I'm a Political Science major and am finishing an internship right now in corporate finance at a large international company. However, it is in credit and collections so I haven't had any relevant experience to investments. My college is a small liberal arts school whose only business major is economics. If I were to minor in Econ, my GPA would suffer due to the major's exceptional rigor--is it worth it? As I head into my sophomore year, I am looking for advice as to if it is possible for me to set myself up to be a good candidate for an IB job, and if so, how do I get hired for relevant internships?