This is an excellent question. There's no worry about being sued.
Let's look at the dictionary definition of "lie:" a false statement made with deliberate intent to deceive.
It is the question of intent that I have trouble with. I have to deal with the facts. How can I prove that a politician intended to deceive people? In some cases (see Paul, Ron), some of these statements, no matter how wacky, come from deeply-held beliefs. The best thing I can do is show how, based on the facts, these statements are inaccurate.
Hence we use a scale of Pinocchios. A reader could decide that a four-Pinocchio statement, made repeatedly, is a "lie" under the dictionary definition. But that's a judgement for you to make, not me.