President Donald Trump's longtime personal lawyer Michael Cohen is thought to have a long history of covering things up for Trump.

People close to the president worry the dirt could come out now that Cohen is under criminal investigation.

"People are very, very worried," a former Trump campaign official told the news website Axios. "Because it's Michael [effing] Cohen. Who knows what he's done?"

President Donald Trump has been visibly fuming about an FBI raid on his longtime personal lawyer and has unsettled his closest allies, according to a new report from the news website Axios.

"The guys that know Trump best are the most worried," a former Trump campaign official told Axios. "People are very, very worried. Because it's Michael [effing] Cohen. Who knows what he's done?"

Cohen has worked for Trump for a decade and has been linked to payments to women who have said they had affairs with Trump. Cohen is "a potential Rosetta stone to Trump's final decade in private life," Axios said.

"People at the Trump Organization don't even really know everything he does," the source told Axios. "It's all side deals and off-the-books stuff. Trump doesn't even fully know — he knows some but not everything."

"I'll tell you who's worried: the principal," the source concluded.

Cohen is under criminal investigation over his business dealings after saying he personally made a payment to the porn star Stormy Daniels, who was paid to keep quiet about an affair she says she had with Trump.

Daniels, whose real name Stephanie Clifford, told reporters that Cohen "for years" acted "like he is above the law" and had "openly referred to himself as Mr. Trump's fixer."

Daniels' lawyer, Michael Avenatti, gave an ominous warning to Cohen on Monday.

"I said last Friday and this weekend that Michael Cohen was radioactive and that anybody that was associated with him in the last 20 or 30 years should be very, very concerned," he told reporters at an impromptu press conference following the day's proceedings.

As investigations into Cohen and Trump simultaneously heat up, a second source told Axios that Trump's "worries about Cohen are reflected in his dark moods."