What is the error on the presidential dollar?

Excuse me, could you please clarify what you mean by "the error on the presidential dollar"? Are you referring to a specific issue or misprint on a particular dollar coin featuring a presidential portrait? If so, could you provide more context or details about the specific coin or series of coins you're referring to? There have been several different presidential dollar coin series issued by the United States Mint, and errors or variations can occur on any of them. Without more information, it's difficult to give a precise answer to your question.