"How do you know a politician is lying?" goes the old joke. "Because his mouth is moving."
Hans Noel, of Georgetown University, has a better answer:
How do you know a politician is being dishonest? He blames something on “special interests.”
What is a special interest? Why, it is an interest opposed to the “general interest” or collective will. But see items #2 and #3 above: There ain’t no such thing.
Special interests are labor and business. They are environmentalists and developers. They are pro-life and pro-choice activists. They are gays and they are fundamentalist Christians. They are you. They are me. It is hard to think of any political outcome that does not satisfy some interests and oppose others....
Yet the point remains: interests are just interests. They are not so special. The founders understood this. James Madison, in Federalist 10, worried extensively about the threats of “faction,” by which he did mean something like special interests. But Madison also understood that this was a natural feature of politics: “Liberty is to faction what air is to fire,” Madison wrote. Rather than insisting that no politician ever bend to the will of a faction, Madison advocated a system, our system, in which factions were set against each other. In a large and diverse republic, with a separation of powers, no one faction could control all of government without being checked by other factions.
This is point eight of a very good ten-point article here.
Another useful heuristic for judging a candidate's political rhetoric is to ask yourself, "why does he/she want this job?" File this under "things to keep in mind in 2012."