I want to say it has something to do with Gubernatorial Elections.
This was probably the most "on the right track" guess. It's a map (as of April 16th) of which states do and do not have statewide mask mandates, which is obviously influenced by the partisanship of the governors.
I want to say it has something to do with Gubernatorial Elections.
Vermont is what messes things up, unless there’s something I’m missing. Maybe it’s states by who the governor voted for, though I’d think WV would be red in that case)
That's an interesting note too because the handful of Republican governors who are blue are mostly more on the moderate wing. The two red Democratic governors (WI and KS) had mask mandates overturned by other branches of state government.