Good point Josh. Perhaps I should define terms, at least the way I see them.
I think "Independent" is perhaps a better term than "Non-partisan." At any given time an independent may favor one party or another (depending on who is in office, and where the party platform is at the moment)...so I suppose at that moment they could be considered "partisan" in their leanings. But they would not have the same loyalty and commitment to a party's ideology and candidates that a true partisan would have, and they might just as easily lean the other direction down the road. There are certainly independents who support Trump right now - and independents who don't. An independent probably wouldn't say, for example, "the Republican party is the more noble party," but they might say "President Trump is the more noble candidate."
"Moderates," on the other hand, are self-identifying liberals or conservatives who are inclined toward the center of the political spectrum. They will generally vote the party line, but as I mentioned, they tend to be less reactionary by nature, and have a higher confidence in established systems, regular order, and the rule of law. They are also more prone to compromise with the other party, or cross party lines, to get things done or follow their conscience.
A "Non-partisan," in my mind, is different from and "independent" because it is a person who is somewhat engaged in current events, but deliberately works at remaining aloof from political allegiances, ideologies, and candidates - perhaps even from voting. This doesn't preclude them from passing judgement on a particular issue or candidate one way or the other - but they wont pass judgement according to a party template. I think you are right - this represents a quite small group of people - although we do have a number of them on MN.