“I think if you add up all the internships in political science each year a minority would be in DC.”
But if you look at the concentration of opportunities year round - the aggregate number of internships in DC in political science/advocacy - I doubt there is anywhere better in the entire country. And summer is when students who live outside of the DC area do their internships (often in DC). Those who are studying in DC often are involved year round. That’s part of what makes it such a vibrant and dynamic place for people with those interests.
That doesn’t mean internships don’t exist elsewhere in the country - they are indeed available everywhere. But what’s special in DC is that there are so many people with a shared interest in how the political process works, such varies opportunities, and so many resources for people who want to learn about the process by actively participating all year round.