I don't think there is any difference between how celebrities, politicians, and private citizen images are allowably used.

It's one thing to satirically use a likeness of a person.  Selling that likeness is a whole other issue. I'm not 100% sure, butI don't think there's anything in copyright or trademark law that defines different allowances for infringement based on whether a person is a celebrity or politician or private citizens. There is a difference in how those individuals decide to protect the use of their images. A politician may decide not to go after infringers because their earnings are based on their political positions and doings, so they might not be vigorously defending their likenesses.  It doesn't mean that they cannot.

My visual indexes of Poser content are at http://www.sharecg.com/pf/rgagnon