I think they're effective insofar as proposals for reform are often deflected by allegations of fraud and deliberate waste - 'if you can't root out the rampant fraud why should we trust you to reform a broken system?!'

You see this argument in immigration politics a lot too - 'we can't discuss reform until the border is secured.' I agree that meaningful reform would probably substantially reduce the profitability of fraud and make it easier to detect as well, but that's political reality for you.