All counselors praise the counsel they give, but some give counsel in their own interest. Be wary of a counselor, and learn first what is his interest, for he will take thought for himself. (Sirach 37:7-8)
This is a good rule to apply to politicians. They are trying, after all, to sell us something. They will always, "Praise the counsel they give" and we would do well to be wary of what we are told, to check what the interest is of those who are running for they will take thought for themselves. And what is it that they want? They want the power of the position they are running for and they will tell us whatever they need to in order to obtain that. Between the two parties we will be told slightly different things because of the base constituencies of the two parties (each constituency must be told what they want to hear) but the message will be tailored to the hearers and does not necessarily represent the reality of what they will do after they are in office and no longer require our input to get there (or at least do not require it for another few years).
When I buy a car I expect to be told many wonderful things about the car I am looking at by the dealer for that car. Do I trust those things? I'd have to be a fool to do so without question. Likewise with these politicians. But it seems that we don't actually apply this rule very often, except to whatever side it is that we disagree with. If we disagree with a politician we will be likely to guess that he/she is just spinning and become cynical and distrusting but if we agree with a politician we suddenly become artless and naive and buy into whatever it says on their web site (copying and pasting it freely to our friends on the other side in the hopes that they, too, will be as trusting of our candidate as we are). We would do well to remember that our own side is selling something as surely as the other side is and doubt accordingly.