Alan Dershowitz believes that Special Counsel Robert Mueller is preparing to subpoena President Trump to appear before a grand jury as part of his ongoing Russia investigation, but Gregg Jarrett isn't so sure.

In an interview Tuesday on CNN, Dershowitz said he thinks Mueller's team is "gearing up for what will be a difficult legal battle."

"You can’t compel the president to sit down with the special counsel, but you can compel him to come in front of a grand jury," he said, explaining that the courts would decide if Trump has to testify.

Jarrett, the bestselling author of "The Russia Hoax," said on "Outnumbered" Wednesday that he's not sure Mueller "has the appetite" for a legal battle in the federal courts.

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He said Mueller is a smart man and he realizes that in the end, in front of the Supreme Court, he would likely lose, which would only further diminish his "increasingly diminishing credibility."

"Mueller's the guy who sabotaged his own investigation," Jarrett said. "First, by refusing to recuse himself in the face of mandatory disqualifying conflicts of interest. And then, [by] assembling a team of partisans."

He said that's why so many Americans are questioning Mueller's ability to conduct a fair, impartial probe.

Marie Harf pointed out that the most recent Fox News poll actually showed Mueller's approval rating up 11 points.

"If we want the truth and the whole truth and nothing but that out of this investigation that we've spent months on and a lot of money on, there are many questions only Donald Trump himself can answer," Harf argued.

.@GreggJarrett: “You can’t question a president’s constitutional authority in firing somebody like James Comey.” pic.twitter.com/7oB5Xt3s9R — Fox News (@FoxNews) August 29, 2018

Jarrett questioned what legal basis Mueller has to question the president.

“You can’t question a president’s constitutional authority in firing somebody like [former FBI Director] James Comey," Jarrett said. "And on what legal basis do you have to question a president about this non-crime called collusion?"

Watch more from "Outnumbered" above.

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