Failed presidential candidate Hillary Clinton may still be considering a shot at the White House, according to Mark Penn.

In a new Wall Street Journal op-ed, the former Clinton adviser wrote that "Mrs. Clinton will easily capture the 2020 nomination."

Penn said Monday on "Fox & Friends" that many Democrats believe Clinton was "unfairly denied" a victory in 2016.

"She's a pro and she learns, and Clintons never stop until they get where they want to go," he said. "And I say don't count her out, and if she gets in she will be quite formidable."

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Penn said he believes Clinton will try to skip as much of the year-long run-up to the first 2020 primary as she can, and then re-energize the Democratic base's core.

He added that if she gets the nomination, the 2020 race will be "the biggest rematch in history."

"Presumably, she would learn that maybe she could take back some of those mid-western voters if this is what comes to pass."

White House counselor Kellyanne Conway tweeted Sunday in response to Penn's piece, seemingly hoping that Clinton does in fact run in 2020.

Penn said Monday, though, that he believes Conway actually doesn't want the situation to come to fruition.

"I think they want to run against Bernie Sanders or Elizabeth Warren. I think Hillary Clinton would be a lot more formidable," he said.

Watch more above.

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