Jack Welch, whose tenure at General Electric made him a management icon in the 1990s and 2000s, has been a huge fan of President Trump's.

A longtime Republican supporter, he got behind Trump last year, praising his plans for tax cuts, regulatory reform and aggressive stance on terrorism. He's been called a member of Trump's “kitchen cabinet” and lauded his business-minded approach to the presidency, saying on cable TV it's “like talking to a peer.” Welch raised eyebrows in 2012 for claiming the Obama administration had skewed the jobs numbers; Trump frequently referred to the government's unemployment figures as being “phony” before becoming president.

The former chief executive, now 81, is still a big fan of Trump's policies, saying on CNBC Wednesday morning that he would give the president an “A” for things like his Cabinet selections, his agenda and the business community's confidence. But Welch also had some sharp words for how the president is running the White House, calling Trump's approach to firing Comey a “rookie mistake,” questioning his handling of messaging and communications and giving him an overall “D-minus” when it comes to managing the federal bureaucracy.

“I think without question we've got a guy that's on the right agenda with crappy management practices,” Welch said on CNBC. He suggested he would give Trump a “D-minus” for management. “And,” he noted, “I'm being an easy grader here.”

Welch started with Trump's approach to firing FBI Director James B. Comey last week, which was done from afar — Comey was reported to have learned about his firing from a television news broadcast while addressing FBI employees.

“I don't want to argue whether Comey should have been thrown out or not. But clearly you don't fire him the way Trump fired him,” said Welch, who is now chairman of an eponymous online MBA program at for-profit Strayer University. “Clearly you don't make any friends doing it the way he did it. There's going to be retribution. It's a minor league — it's a rookie mistake.”

Welch then seemed to compare Trump to his predecessor. “You've got to give Obama credit. There was no trouble on that team,” Welch said. “He had that team around him. They spoke with one voice.”

Returning to Trump, he said, “He set a great mission: Make America Great Again. Get jobs back. Strong military. Lead the country. He had the mission. Now you align the troops around the mission, everybody buys it. If they don't get on the bus, throw them the hell off the bus.”

Welch appeared to go on to presume that Trump knew who was leaking information, and that Trump would be able to fire them. “Why he's letting these people that are leaking everything hang around,” he said, “it's crazy management.”

One of the “Squawk Box” hosts asked Welch whether Trump should have known that from the business world, or if political leadership was a different thing. “No, I think he was an entrepreneur who ran his own shop,” Welch said. “He never ran a bureaucracy, in my opinion. If you run a bureaucracy, they're in the weeds. They're behind the desk. They're whispering at the water cooler. You've got to nail them and get them the hell out of there. And he didn't do that.”

Welch also criticized Trump's handling of his communications team. “You've got to get your communications team all together with you, and they've got to live with you, so everybody gets the same message. Everybody speaks with one tongue. This is crazy. He says one thing, they say something else, and the press has a party.”

Welch appeared to be referring to the shifting explanations Trump and his team have made regarding Comey's firing, as well as on Trump's sharing of classified information during an Oval Office meeting last week.

Though critical of Trump's management of the White House, Welch, a member of Trump's business advisory council, is clearly still a fan. “I love the people he's picked: Betsy DeVos, Scott Pruitt, the military side, Rex Tillerson. I love those people. I think they're great,” Welch said, adding “there's an air of confidence” in the business community and among consumers. Welch also referred to the Russia story as one of “these little things” and said he thought any impeachment proceeding would “blow the market away.”

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