Sorry I can't be more specific, as it's been more than a decade and I've experienced the onset of cognitive issues, and all links and records I have are no longer on my computer nor easily accessible.
Start with the Challenger and Columbia accident reports, the annual budget asks and appropriations over the years, plus a number of different reports about NASA and how it's operated in relation to Congress, the Presidents, and the aerospace industry. The Wikipedia articles on the Iron Triangle and Project Management Triangle are very brief introductions to the concept. I'm sure a search for NASA with those terms would turn up appropriate links.