One of the aspects of campaign commercials that I hate is "spin". It's use of "almost-truth" to shore up your candidate. One stat that is often used is deportations.
This article explains why many of the ads/news articles (too often, the same thing) can generate such different numbers, when discussing the same things. These very different numbers lead to the opposing conclusions that fuel the accusations of lying.
Neither side is technically lying - but, in many cases, one or BOTH are playing with definitions, using stats misleadingly, or extending a trend beyond what the data can justify (the "hockey stick" example).