Really no way to know for certain......the overwhelmingly Native counties could give us some clue, but without precinct data it'd be impossible to get anything resembling an accurate overall tally.
As to the major reservations (of actually Native population, not the overrun ones), they've been overwhelmingly Democratic, with very low turnouts, ever since news about federal events started reaching them. Until the 1920s they didn't have the vote at all, and in between there's a short time window where they voted for whichever party controlled access to information - the Sioux rezs voted Republican in the 20s and 30s IIRC.
Ah, ok. So what you are saying is there are very few heavily Native precincts offrez. That makes sense then.
