Adding to this, there are many many House races (435 voting members!) and there are always going to be some surprise wins or almost wins from challengers, where the DCCC provided no support, that can lead people like me to cry foul. It's just going happen "randomly" sometimes. But watching this every election cycle, I think it's correct that these candidates are almost always "too liberal" candidates, certainly perceived as "too liberal" for their districts, who didn't start with their own obvious funding base, and often ones who beat the party's (state or DCCC) favorite in the primary.
