New York Mayor Bill de Blasio, considered one of the most liberal public officials in the country, warned fellow Democrats not to underestimate famed neurosurgeon Ben Carson.

“I think Ben Carson should not be underestimated. I get very worried as a Democrat when we underestimate Donald Trump or Ben Carson or anyone,” de Blasio said Friday on MSNBC’s "Morning Joe."

“Ben Carson is a really impressive human being," de Blasio added. "Let’s just face it. He’s a very accomplished man. I think his calm demeanor is something people appreciate in a very contentious moment.”

Explaining how Carson has defied the pundits, de Blasio said, "He also is the ultimate outsider, because here, he is accomplished in the medical field who did something that’s not politics, that’s not Washington and it is the antithesis of what is happening. People shouldn’t forget that the public is being logical on one level that they like something that is very different from what they see in Washington.”

However, de Blasio made sure to note that Carson should be disqualified.

“I think some of the things he said, for example, about Muslim Americans, are absolutely unacceptable,” de Blasio said. “I think they will ultimately disqualify him. But don’t go to sleep on someone who is accomplished and impressive.”

The mayor, who worked on Hillary Clinton’s 2000 Senate campaign, endorsed her for president during his appearance on the program after holding off for several months. Still, he asserted as a progressive, he endorsed her “enthusiastically.”