What is an example of an ad hominem argument?

An ad hominem argument is a logical fallacy that occurs when an individual attacks the character, motives, or other attributes of a person making an argument, rather than addressing the argument itself. In this context, the choice stating that "Steve Forbes has changed his stance on fiscal policy" implies that Steve Forbes is inconsistent or unreliable. This assessment does not engage with the actual content or merits of his fiscal policy stance but instead focuses on his character or behavior.

This is classic ad hominem reasoning because it attempts to undermine his argument by pointing out a perceived flaw in him as a person (his inconsistency), rather than discussing the substance of his policy proposals. Addressing a person's credibility or personal history to refute their argument without engaging with the actual argument is the essence of ad hominem reasoning.

In contrast, the other choices do not exemplify this fallacy. They either present facts or opinions about the subject without attacking a person’s character or consistency. Thus, the correct identification of an ad hominem argument aligns precisely with the provided answer regarding Steve Forbes.