I've never seen numbers for 2024, but I have for previous recent national elections, and the most either party has in any state is roughly 70%. So at the statewide level, that's the total skew you're looking at.
In local elections, things can be more one-sided; I imagine there are a fair number of rural counties that would have only a handful of blue voters (but out of a total of, y'know, a few thousand voters in the whole county).
I'd like to have fine-grained data on the "purple" states. For 2024 there's, eg (not even collated policy data, but it's something)
http://www.cookpolitical.com/analysis/national/national-poli...