The state doesn't appear to have an ancestral democratic domination like many areas in the south, so why are there so many registered democrats there?
Oklahoma abandoned the Democratic party a lot earlier than other Southern states in Presidential elections. But local offices were still competitive between democrats and republicans despite that. As with the national geographic realignment and the Southern local parties. The local branch declined eventually but a lot slower than the national democratic party. However a lot of people who registered democrats who might not of voted democrats they changed registration a lot slower than for example neighboring Texas which also used to have a democratic plurality of the registered voters. And thats mainly because the process in Oklahoma was for a long time having to go to a court house to change registration which for many people wasnt worth the process. However if i hear this right, the state government made it a lot easier and the number of registration changes to the GOP from longtime republican voting registered dems is going really fast which made the registration difference from double digits to single digits as of current.