As a political science major, I have spent the last two weeks closely examining the Democratic and Republican Conventions.  I think that politics, especially the conventions is one of the greatest places of propaganda.  They tell you what issues are important and the media shapes the agenda of the conventions.  The conventions are all about great speakers and great "performances" by the candidates and by the supporters of the candidate and the party.  Overall I think politics is the greatest spot to look for the media's use of propaganda.