I am very sympathetic to the idea, but the reason the "Show HN" and "Ask HN" sections are valuable is that these posts are overwhelemed in the main view, rather than vice-versa.

An explicit "Politics" section even if excluded from the main feed or included with a large penalty (Like "Jobs") would probably suck the air out of the rest of the site.

A better option might be a separate politics-oriented site, perhaps hosted by a nonpartisan policy-recommending organization (in itself a tall order).