I like to gather with my friends on campus to talk politics. We have a particular spot that we always use. What happens if I show up one day and somebody is already there and talking about another topic?

If you did not reserve the space for your plans, then the speaker who is there before you has priority in that space at that time. There are plenty of other outdoor spaces on campus – just find another one and go there with your friends to talk politics. And, remember to talk to the Office of Student Involvement about making a reservation for future gatherings of your group.