There is a strong cultural significance surrounding the term propaganda. It is manipulative, it appeals to base desires, and is most associated with the ideological authoritarian regimes of Hitler, Stalin, Saddam Hussein, etc. So propaganda is a term we use to denigrate communication, to question the validity of the substance as opposed to the objectives of the communicator. Thus, from the US, mayor Jan Mill's communication is described thus by an opponent: "I felt like it was just simply political propaganda simply because it was filled with mis-statements about the truth." Apart from the wonderfully hedged phrase "mis-statements about the truth", does this miss a fundamental point?
According to one online dictionary propaganda is "the spreading of ideas, information, or rumor for the purpose of helping or injuring an institution, a cause, or a person (or) ideas, facts, or allegations spread deliberately to further one's cause or to damage an opposing cause; also : a public action having such an effect." The key points here are the idea of propaganda being communication that deliberately helps or injures a cause. So it could be lies, exaggerations etc, or it could be facts.
Taking a current example, by focusing on the age of Menzies Campbell, both media editorials and members of his own and opposition parties deliberately undermined his position. The fact that he was unable to rebut those comments made the campaign successful. The fundamental idea here is that propaganda is basically communication with a purpose, that purpose being to affect the attitudes, opinions, beliefs and behaviour of receivers. So we could argue that every newspaper that offers a biased argument, every slanted piece of news that offers facts from a single perspective, every person who tries to make themselves appear better than they really are (which we all do), and every party that spins is doing propaganda? Can't we?