It is "ludicrous" for New York City Mayor Bill de Blasio and others to say that 2020 presidential candidate Joe Biden hasn't been vetted, Fox News contributor Jessica Tarlov said Tuesday.

Appearing in a panel on "America's Newsroom" with host Ed Henry and Josh Holmes, Senate Majority Leader Mitch McConnell's former chief of staff. Tarlov said she doesn't think anyone is "rushing" about endorsing the former vice president.

"The idea that Joe Biden hasn't been vetted when he has been a senator, he's been a vice president, where he did go through a vetting process and he went through debates, is ludicrous," she stated. "And Bill de Blasio is really grasping at straws here to try to find something."

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Appearing on MSNBC's "Morning Joe" with host Joe Scarborough, De Blasio said 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," said de Blasio, a backer of socialist Sen. Bernie Sanders.

"What he didn't say outwardly – but you know is implicit in what he's saying – is he is becoming part of this 'Biden has dementia game' where people are arguing that he doesn't have the mental fitness to make it," Tarlov replied. "That once he gets on stage with Donald Trump, it's going to be a disaster. And, it's not just gaffes but it's actually cognitive decline that is irreversible and people need to be paying attention to this."

"This is a sick rumor," she urged. "I think it's disgusting and baseless and you can see a unification of 'Bernie Bros' and people who support President Trump around this."

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"I think it absolutely needs to stop," she told Henry. "Joe Biden has been making the 'gaffes' that he is making today for decades. There is tape of it."

Tarlov later concluded that while de Blasio didn't accuse Biden of that outwardly, she was suggesting that was his intention in making those remarks.