Yes, it is possible, but it takes a discerning and alert audience to do so. The two ARE black and white, but a skilled public speaker will make them seem gray. He or she will skillfully combine opinion with fact, and utilize this to draw the jury to the conclusion where he wants them to arrive. It is up to the jury to be able to draw facts from the arguments, and base their decision solely off that.
People turn to patternicity when their schemas are not fully filled in (such is the case with the predator-in-the-grass example). Thus, politicians are more liable to utilize it to their advantage on topics that people are uneducated about. I agree with Lauren in that the Type II style is used more often, as politicians prefer to substitute the real reality (or pattern) for their own.