MSNBC host Chris Matthews offered interestingly high praise for White House hopeful Bill de Blasio during Wednesday's first Democratic primary debate, saying the New York City mayor was "surprisingly a heavyweight."

Matthews began by declaring that former Vice President Joe Biden was the "winner" of the debate since none of the 10 candidates on the stage went after the Democratic frontrunner. He also complimented the performances of Rep. Tim Ryan, D-Ohio; Sen. Elizabeth Warren, D-Mass.; Rep. Tulsi Gabbard, D-Hawaii; and former Housing and Urban Development Secretary Julián Castro.

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The "Hardball" host then pivoted to the mayor, with whom he said he was "really impressed."

"I thought that de Blasio was surprisingly a heavyweight tonight," Matthews told the panel. "I think he entered into the national debate coming from New York City and joining right in with the national debate about war and peace and the big issues. I was really impressed with de Blasio tonight."

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Other panelists were not as kind to the mayor. MSNBC contributor Claire McCaskill, a former U.S. senator from Missouri, said de Blasio was "mildly irritating."

"I had the same reaction," MSNBC host Nicolle Wallace said. "He sounded to me like sort of an obnoxious guy at a restaurant or a bar talking really loudly like everyone wants to hear what he's saying. Like, I wanted to hear other people's answers and he kept butting in."