Legal experts, as well as Trump's allies and confidants, think Cohen is already in deep trouble and headed for even more. Cohen's home, office and hotel room were searched last week in a series of raids by FBI agents.
The besieged fixer, who has handled Trump's legal affairs for years, could be facing a choice between prison time or cooperating with federal prosecutors.
On Thursday, Trump's former divorce lawyer, Jay Goldberg, told The Wall Street Journal he has warned the president that Cohen's loyalty to Trump would be compromised if Cohen faces criminal charges.
Goldberg said he told Trump that Cohen "will never stand up" for him.
On a 1-to-100 scale, where 100 is fully protecting the president, Goldberg said he told Trump that Cohen "isn't even a 1."
After Cohen's residence, hotel room, office, safety deposit box and electronic devices were raided April 9, Trump's advisors began to fear that the investigation posed a greater threat to the president than special counsel Robert Mueller's probe of potential links between Trump's campaign and the Kremlin, The New York Times reported.
Federal agents seized materials that included documents related to women being paid for their silence about alleged affairs with Trump, as well as files relating to communications between Trump and Cohen.
The search warrants, signed by Deputy Attorney General Rod Rosenstein, were based on a referral by Mueller.
Trump is being sued by porn star Stormy Daniels, who seeks to void a nondisclosure pact negotiated by Cohen shortly before the 2016 election, which barred her from discussing an alleged affair with Trump. Files related to Daniels were among those seized from Cohen.
Trump has denied the affair ever occurred. After the raids, he blasted them as being "an attack on our country in a true sense."
The investigation into Cohen "is very serious," said Harry Sandick, a former assistant U.S. attorney for the Southern District of New York.
Sandick, now in private practice, told CNBC that government filings in the case "indicated to me that this was not an investigation that just began 15 minutes ago."
"Cohen should be very concerned. He's the subject of a long-term investigation by the Southern District of New York, which has a strong record in cases of white-collar and other crimes."
The filings indicate that Cohen had been under suspicion by prosecutors for months, and that his email addresses had been secretly monitored for some time before the raids.
Cohen "seems to be at the nexus of a lot of things with Trump, and now there's a chance he could be prosecuted," Sandick said.
The former prosecutor said that if Cohen is charged, information that he offers prosecutors in exchange for some kind of leniency or plea deal would not be limited to the crimes that authorities believe Cohen committed.
And that could spell trouble for Trump.
"If a guy's going to cooperate, who knows where that leads?" Sandick said.
One reason that Cohen might cooperate is if he feels that he is being made the scapegoat for misconduct by others.
Sandick noted that in the days before the raids, Trump denied knowing about a payoff that Cohen made to Daniels. That payoff is being eyed by prosecutors.
"It certainly shows that Trump had no hesitation to put this on the shoulders, on Cohen's shoulders," Sandick said.
Trump's strong denunciations of the raids could betray an anxiety about Cohen's susceptibility to becoming a cooperating witness, Politico noted Thursday.
Unfortunately for Trump, much of the speculation has been built on the presumption that Cohen is likely to get criminally charged — and if so, will have concrete information to give prosecutors about potentially criminal actions by the president.
Both Goldberg and James Comey, the FBI director who was fired by Trump fired last year, have made analogies to the mafia while discussing Cohen and the president.
"The mob was broken by Sammy 'The Bull' Gravano caving in out of the prospect of a jail sentence," Goldberg told the Journal.
Comey, in his newly released memoir, said the president's demand for his loyalty during a White House dinner last year "was like Sammy the Bull's Cosa Nostra induction ceremony."
Alan Dershowitz, the famed lawyer who often supports Trump on television interviews, told Politico that prosecutors are "going to threaten [Cohen] with a long prison term and try to turn him into a canary that sings."
Dershowitz met with Trump and his staff twice in the last week, Politico reported.
Lawyers for Cohen and Trump did not immediately respond to CNBC's request for comment.