Former Office of Government Ethics Director Walter Shaub Walter Michael ShaubTrump breaks with precedent on second night of convention Democratic senators call for ethics review into Ivanka Trump's Goya tweet Chris Cuomo blasts Trump over photo with Goya products: 'In the middle of a pandemic, they're selling beans' MORE ripped President Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE's tweet Saturday saying he was "very smart," claiming the tweet would be enough for corporate boards to hold an emergency meeting on a CEO's mental health.

"Forget the book. This might be enough to lead the board of any corporation to call an emergency meeting on its CEO’s mental status," Shaub wrote, quoting the president's tweet.

Shaub, who clashed with the president over his business interests, resigned from his government post last year.

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Trump fired off several tweets Saturday morning defending his mental fitness after the topic bubbled up this week following author Michael Wolff's new tell-all book, "Fire and Fury: Inside the Trump White House."

The book includes a claim that concerns about Trump's mental fitness are shared even among his top aides.

“My indelible impression of talking to them and observing them through much of the first year of his presidency, is that they all — 100 percent — came to believe he was incapable of functioning in his job,” Wolff wrote.

The White House has hit back against the claim, calling it "outrageous."

"It's absolutely outrageous to make these types of accusations and it's simply untrue, and it’s sad that people are going and making these desperate attempts to attack the president,” White House press secretary Sarah Huckabee Sanders told "Fox & Friends" on Friday.