I'd expect most challenger parties to be less corrupt than an incumbent party that had held power for a long time, at least for a while, and maybe for a long wh

I'd expect most challenger parties to be less corrupt than an incumbent party that had held power for a long time, at least for a while, and maybe for a long while if their hold on power remains more tenuous than the incumbents' had been. I'd expect this to be especially true at the local level, where the money involved in running a challenger party operation and campaign is unlikely to be high enough to support much corruption before office is taken.