After the first day of the Democratic convention was frequently interrupted by delegates for Sen. Bernie Sanders (I-VT) protesting calls to unify behind Hillary Clinton, the Vermont senator told his supporters Tuesday that their jeers would not stop a Donald Trump presidency.

During a breakfast meeting with California delegates, attendees booed when Sanders said that they need to elect Clinton and defeat Trump. The senator then told the crowd that their jeers aren’t helpful.

“It is easy to boo, but it’s harder to look your kids in the face who would be living under Donald Trump,” he said.

Sanders went on to call Trump “a demagogue who does not believe in the Constitution of the United States.”

“That is dangerous stuff. So our job is to do two things. It is to defeat Trump, it is to elect Clinton. But it is not to end on Election Day,” he said.

During a morning event held by Bloomberg Politics, Sanders said he hoped his supporters would “accept the reality” that Clinton will be the Democratic nominee.