Remember that you're free to use any prefix you want to invent. If you want a "Pol" prefix, just type it in. If people like it, then maybe others will start using it. I see that's happening already with the caption threads. We've long had a policy that requires that thread titles reflect what's inside the thread, so we routinely add clarification to thread titles that are unclear. I think that generally, people can easily tell which are the political threads, so I personally don't see a need for a special "pol" prefix.
-Joe-