George Conway, a lawyer married to White House counselor Kellyanne Conway, argued Tuesday that special counsel Robert Mueller's report must have "something pretty damning in it" if it could not exonerate President Trump on the question of obstruction of justice.

Conway, a frequent critic of Trump who recently feuded with the president on Twitter, wrote in an op-ed in The Washington Post that it was "stunning" for Mueller to include a line in his report stating that "while this report does not conclude that the President committed a crime, it also does not exonerate him."

"Mueller didn't have to say that. Indeed, making that very point, the president's outside counsel, Rudolph W. Giuliani, called the statement a 'cheap shot,'" Conway wrote. "But Mueller isn't prone to cheap shots; he plays by the rules, every step of the way. If his report doesn't exonerate the president, there must be something pretty damning in it about him, even if it might not suffice to prove a crime beyond a reasonable doubt."

Mueller's report has not been released publicly, but Attorney General William Barr on Sunday shared a summary of what he described as Mueller's "principal conclusions," revealing that Mueller did not find evidence to establish that members or associates of the Trump campaign conspired or coordinated with the Russian government to interfere in the 2016 election.

According to Barr, Mueller also "ultimately determined not to make a traditional prosecutorial judgment" regarding whether Trump attempted to obstruct the probe itself - leaving the decision up to the Justice Department.

Barr wrote that he and Deputy Attorney General Rod Rosenstein determined that the evidence was "not sufficient" to establish that Trump obstructed the investigation.

Conway argued that, based on the Justice Department summary, Mueller wrote his report in such a way that allows "the American people and Congress to decide what to make of the facts."

"Americans should expect far more from a president than merely that he not be provably a criminal," Conway wrote. "They should expect a president to comport himself in accordance with the high duties of his office."

Conway highlighted Trump's frequent public attacks on Mueller, former Attorney General Jeff Sessions and other Justice Department officials throughout the nearly two-year investigation.

"If the charge were unfitness for office, the verdict would already be in: guilty beyond a reasonable doubt," Conway concluded.

Conway has emerged as one of the president's most frequent critics, despite his wife's high-ranking position in the Trump administration.

Trump responded to the lawyer earlier this month, sharing a tweet from his campaign manager Brad Parscale accusing Conway of being jealous of his wife and calling him "a total loser!"

The men have continued to trade barbs on Twitter, with Trump calling Conway the "husband from hell" and a "whack job" and Conway calling Trump "nuts."

Kellyanne Conway has stood by the president, saying her husband is not a medical professional and should not be questioning his mental fitness.