Political parties are constantly using attack ads to shed negative light on opposing candidates. In many of those ads you can find a black and white filter, an ugly picture of the other candidate, and aggressive music playing in the background. These effects are added to sub-consciously give viewers the idea that this person represents only bad things and is clearly not the one they should be voting for. Another way they may convince you of this is by using logical fallacies in their argument. One very common fallacy used in attack ads is Ad Hominem which is essentially attacking someones character rather than the argument the person is advancing (or rather, their ability to fulfill the duties their elected position would require them to do). An example of Ad Hominem in an attack ad is one created by Taxpayers for Quinn, who are attempting to persuade Illinoisans that Bruce Rauner is a billionaire that isn't realtable to the average man and, therefore, a poor choice for Illinois governor. They do so by attacking his character rather than directly stating why he lacks the ability to govern.
The ad states that Rauner outsourced jobs to China which is actually an important piece of information for an informed voter however, it also attacks his character by mentioning that he stashed his own money to avoid paying higher taxes. What he does with his own money has little to do with his actual ability to govern Illinois. Instead, it gives the audience a clear and simple idea of what Rauner's moral are. The ad also shows its audience that Rauner isn't a normal guy and isn't for the normal guy by stating that he joined an elite wine club for 140,000 dollars. Although the audience may look poorly on him, that fact gave them no information on how he plans to lead a state full of middle class citizens when he himself is a billionare. The commercial used Ad Hominem fairly effectively because it would be difficult to watch this attack ad and them think fondly of Rauner.