Yes, users with very strong political leanings and an even stronger desire to spread them are a regular appearance on this website.
Unfortunately, it is impossible to tell if these people are paid by some government or non-government organization or if they are just private people who very strongly believe in some political cause and spread it in their free time. I don't think it is very likely that Politics Stack Exchange is being targeted directly by any organized propaganda operations, though. We aren't Facebook, Twitter or Reddit. Our community is still relatively small. I think it flies far under the radar of any serious propaganda organisations. We might of course still see some indirect effect of these efforts in form of regular people who got radicalized somewhere else and now feel they should spread the "wisdom" to us. But that doesn't make these users any less obnoxious.
Fortunately, the Stack Exchange environment isn't very friendly to these users. Posts with obvious political slant - no matter which direction - often attract a lot of downvotes. Posts which are just political propaganda and include no useful on-topic content often get deleted by the community before we mods get to do it.