Bachelor in Political Science to later study economics? or an inter major?

Basically I want to become a leader, ambassador, president, senator etc but at the same time I think economics is really important. I have always been interested in social studies and took ap in high school. Right now I am in my freshmen year in political science.

My plan is to get a bachelor in political science then study economics. Just like how many study pol-sci like Obama to later study law. How would it work out or should I have started with economics?