I applied online. The process took 6 weeks. I interviewed at Tax Foundation (Washington, DC) in Feb 2020
Interview
Very general and straightforward interview with pleasant HR. The interview didn't really have any out of the box questions and felt generally comfortable. Not a scary experience but prob didn't go very well.
There was a brief phone interview after I applied online. It was fairly straightforward and asked simple behavioral questions. Overall, it was a fairly positive experience. I wish I had learned more about what role the interns have.
Applied online, got interview a few weeks later. Phone interview with current employee; went well and asked typical questions. Asked some questions about philosophy toward economic policy, as well as questions like "discuss a time you've failed"