I got interested enough in the national debt to do some research: is there a single-issue NGO that's working on the national debt? With a platform that you could imagine a Democrat or a Republican supporting?

I found the Concord Coalition [0], and their sister organization Concord Action [1].

I haven't done enough research to endorse them, but I'm just saying: they exist and this is their issue.

[0]: https://concordcoalition.org

[1]: https://concordaction.org/