Washington (CNN) Former Republican Sen. Jeff Flake, whose vociferous criticism of Donald Trump sparked widespread speculation that he could mount a primary challenge to the President, flatly said Tuesday he will not launch a primary campaign against Trump in 2020.

"I've always said that I do hope that there is a Republican who challenges the President in the primary. I still hope that somebody does. But that somebody will not be me. I will not be a candidate," Flake said on "CBS This Morning."

"There really isn't a path, right now, that I can see. Certainly not unless you're willing to be out there already raising a lot of money and basically living on the road right now," said Flake, who represented Arizona before his retirement earlier this month.

The former senator added that he thinks a Republican challenger to Trump is "healthy."

"And I'm not a fan of this President," he said. "But that (challenger) won't be me."

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