Appearing Tuesday on MSNBC’s Morning Joe, New York City Mayor Bill de Blasio, who endorsed Sen. Bernie Sanders (I-VT) for president, warned that Democrat primary frontrunner, former Vice President Joe Biden, has not been vetted.

A partial transcript is as follows:

JOE SCARBOROUGH: I apologize in advance for asking this question, but you’re probably not going to be on tomorrow, so I’m going to ask it today. If the polls are right and if Joe Biden wins handily in Michigan, wins handily in these other states, then Bernie’s pathway to winning the nomination suddenly narrows very quickly. Will there be some point when we move forward in the next few weeks, lets say Joe Biden does as well as he’s expected to do next week in Florida, Arizona, and some of these other states, will you be telling Bernie to consider getting out of the race and supporting Joe Biden?

BILL DE BLASIO: Respectfully, I don’t know anyone in politics who has been counted out more than Bernie Sanders more time. All of 2015 and 2016 we were being told there’s nothing there until he came this close to winning the nomination. This year he was supposed to be an afterthought and he came out of nowhere to become the dominant presence. His ideas are the dominant part of the debate right now. He is literally framing the entire Democratic discussion. Don’t count this guy out.

[…]

I’ll tell you something else. Our candidate needs to be vetted. I am deeply concerned. Bernie’s been started to get vetted quite a bit and that’s important to get ready for the general election. Joe Biden hasn’t been vetted. He was in a perfect position. Early front-runner and then everyone thought he wasn’t gonna make it, turned their attention to [Mike Bloomberg], Bernie [Sanders], even to [Elizabeth] Warren for a while. Joe Biden has a lot of issues he needs to speak to. If we don’t deal with it now, in the family, and have that blunt discussion, Donald Trump will.