It seems that Aristotle's classical view of rhetoric could encompass both rhetoric as an art used to sway audiences and rhetoric as an underhanded political tool. In On Rhetoric, he states, "Speech based on knowledge is teaching, but teaching is impossible [with some audiences]; rather, it is necessary for pisteis and speeches [as a whole] to be formed on the basis of common [beliefs]" (34). Here, Aristotle indicates that rhetoric cannot be completely factual, that to be persuasive it is necessary to appeal directly to one's audience, to use their beliefs and thoughts to one's advantage. This is not a bad thing unless speech is used "unjustly" (34), indeed it is essential for thorough argument of a point, and thorough argument is essential for political action and the creation of new ideas.
Aristotle's description of rhetoric as speech with a "basis of common beliefs" allows for a certain duality in the practice of rhetoric. On one hand, the speaker has something in common with his audience (Roosevelt the manly man, speaking to the men of America and urging them to become more manly) and uses pathos and logical appeal to encourage it to consider and agree with his point of view. Conversely, the speaker pretends to have something in common with his audience (Marie-Segolene Royal identifying with the Socialist party of France but seeming much more conservative in real life) and then uses this pretense to convince the audience of his point of view. It seems that each speaker may use the same tools, but for much different ends, depending on their motivation for speaking and convincing. Thus, while the speaker claims commonality with his audience, there is always a disconnect between what is being said and true "knowledge," even if the speaker is genuine. This can be true for any text, as the reader must consider the author's motives for and influences on his writing, as well as the actual words on the page.