Let's imagine this scenario for a moment.
Say you live in a county somewhere in some state. Your county executive is a Republican, though your county is heavily Democratic in every other way. The only way he hangs on is through the abundance of rich people and members of a certain increasingly-Republican ethnic minority in the county. In addition, elections are nearing so this county executive sees the writing on the wall, and consequently is desperately trying to pivot to the center. However there's a problem, this county executive's challenger is a popular state senator. If he were to become county executive, that would mean giving up his seat in the State Senate, which is likely to be filled by a Republican. The Governor and Assembly are both controlled by the Democrats in this state. Only the State Senate is controlled by the Republicans (hint: even though Democrats are the majority when elected,) and losing a seat would make the task of taking it back more annoying.
What would you do? At this point do you really want to risk it and get rid of that county executive? I'm not so sure anymore. He might have ran an annoying campaign in the past, but in substance he isn't too bad. His platform isn't too different from his Democratic challenger, both say they won't raise taxes. The only significant critical points are that the Republican wants to lease out the local airport to private administrators to fill a budget hole, and he vetoed a bill making the county a sanctuary bill. I'm not so sure.
Does NSG have another opinion? Is a Republican county preferable to a senate controlled by them?