I'm not up on the other counties, but Republican machine in Delaware County has built such a stranglehold organization, you can't do anything unless you're registered Republican.
Want to start a business, get zoning relief, get a fair court hearing, have your elected officials listen to your problem, and of course, do business with or work for, County or Local Government, register Republican.
They're so cocky, they won't even take bribes from non-party members.
But, that's the first half of the problem. Like UT said, "people pull the party lever for those offices as no attention is paid to them", which solidifies their power.