President Barack Obama, who's set to address the Democratic National Convention Wednesday night, urged Democrats to take Donald Trump seriously, saying "anything is possible in November."
"It is the nature of democracy that until those votes are cast and the American people have their say, we don't know," Obama told NBC's "Today" show.
Back in January, Obama firmly rejected the message of Trump's campaign and said he expected as much from Americans.
Asked by NBC's Savannah Guthrie whether he's now "worried" about Trump's candidacy, Obama replied, "I've seen all kinds of crazy stuff happen."
"I think anybody who goes into campaigns not running scared can end up losing," he said.
"So, my advice to Democrats — and I don't have to give this advice to Hillary Clinton, because she already knows it — is you stay worried until all those those votes are cast and counted because you know, one of the dangers in an election like this is that people don't take the challenge seriously. They stay home. And we end up getting the unexpected."