Oh, by the way, I hope no one gets the idea that you're on easy street once you're in a policy department. Some policy departments can be real meat grinders, and politicking can be intense due to the congregation of high CEPers and competition will thus be intense.

What you need is to be well-presented, well-spoken, confident, able to run presentations and talks, and also be able to write good English (in the policymaking sort of language). What passes for mediocre in other departments would likely rank as unacceptable here.