President Joe Biden had a simple response to a question that Nikki Haley seemed to have trouble answering.

At a town hall event in Berlin, New Hampshire, on Wednesday, a voter asked Haley to state the cause of the Civil War. In a reply that went viral, Haley said it was about the role of government and “the freedoms of what people could and couldn’t do.”

“It was about slavery,” Biden offered in a post on X, formerly Twitter, sharing a clip of Haley’s exchange.

Haley, the former governor of South Carolina, was widely criticized for failing to mention slavery in her response, including by the questioner at the town hall, who said, “In the year 2023, it’s astonishing to me that you answer that question without mentioning the word slavery.”

“What do you want me to say about slavery?” Haley countered. “Next question.”

South Carolina was the first state to secede from the Union. In its 1860 declaration stating its reasons for doing so, the state government cited “increasing hostility on the part of the non-slaveholding States to the institution of slavery.”