What font did Obama use?

I'm curious, can you tell me what font did former President Barack Obama use in his official documents or during his presidential campaign materials? I've always been fascinated by the small details that go into creating a strong brand image, and I'm sure his font choice played a role in that. Do you know if there was a specific reason why he chose that particular font? Or was it simply a matter of preference? I'd love to hear your thoughts on this.