The Democratic senator will not vote to confirm the ex-national security adviser, who she says is "failing up" after putting the U.S. at risk with the Signalgate scandal.

"I think it will be a brutal confirmation hearing," Sen. Mark Warner said of Mike Waltz. "I think he's going to have tough questions."

There are some hurdles former National Security Advisor Mike Waltz must clear first before the United Nations ambassador job is his — including undergoing a Senate confirmation process.