This is probably more true on the national level than on the state and local level. Plenty of people get involved at the local levels because they see problems with their community that government could fix. Given that many national politicians started as state and local politicians, one would think at least some of them started with a good moral system
I live in a state with caucus primaries and it prevents any non-party candidates. Even at the local level you get some horrible choices of picking the least bad, corrupt, or even crazy guy.
Luckily, for at least some positions there is not enough party interest and there are 3 or more candidates that have to explain their platform and reasoning. If only that was the case with the more important positions.
Similarly, the Republicans where I live are always sending DC interns to us for state legislature. I guess it is an attempt to give the intern running experience. The campaigns hardly ever seem to be an actual attempt to win.
The area is full of good paying jobs. What that means is the local politicians are usually some rich person's partner. Otherwise the crop is usually public employees with an ax to grind or personal trainers/masseuses looking for a steady income.