Don Jr is reportedly facing indictment in the probe by special counsel Robert Mueller over admissions he met with Russian agents to get dirt on Trump’s election rival Hillary Clinton.
Trump himself is reportedly in an awful mood due to the probe he has branded a “witch hunt” possibly snaring his oldest son.
And Don Jr is reported to have briefed pals he believes he will be pulled into the probe soon, with other US reports suggesting his arrest is “imminent”.
Talk of impeachment has loomed over his presidency, and American political history professor Allan Lichtman told Daily Star Online he believes Don Jr could be enough to bring down the US President.
However, he added he believes Trump may be willing to throw his son “under the bus” to protect the White House.
And the expert – one of the few who predicted Trump’s presidency – said he fears for Mueller after the sacking of attorney general Jeff Sessions.
Lichtman, from the American University in Washington, said it is a “real possibility” that Don Jr will be indicted soon over his meetings during the campaign.
"[Don Jr’s indicment] would send Trump over the edge. Trump has no loyalty to anyone except himself, and the only exception may be his immediate family,” he said.
“Everytime one of his close associates gets in trouble, the first thing he does is throw them under the bus.
“But if the special counsel starts to infringe on his immediate family, that might get him to try fire the special counsel and to issue a pardon to Don Jr.”
Democrats reportedly see firing the special counsel as a red line on attempting to launch impeachment proceedings against Trump.
Donald has admitted Don Jr had the meeting with Russian government-linked sources at Trump Tower, but denies any wrongdoing.
He, along with Jared Kushner, the now-jailed Paul Manafort and others, were there to discuss getting “dirt on Clinton.
The US President’s son then lied about the meeting, claiming it was about adopting Russian kids in the US.
Leaked email exchanges then confirmed the real purpose of the meeting – which Trump then admitted to this August.
“Don Jr would probably be facing a charge of conspiracy against the US which would come with it serious jail time,” Lichtman said.
The expert, who authored book The Case for Impeachment, added however he believes Trump may not protect Don Jr if he is implicated in collusion with Russia.
He said pointed how Trump has been willing to distance himself from previous allies implicated in the Mueller probe – such as Manafort.
And he noted how quickly the US President was to turn on his lawyer Michael Cohen over allegations of hush money paid to Stormy Daniels.
Lichtman said: “There are lots of reports coming out of White House about how angry and frustrated [Trump] is, I think he realises the special counsel is tightening around him.”
“What will be most telling is when Trump starts becoming isolated, starts refusing the answer questions, not giving interviews, not turning up to events – and we are seeing some of that now.”
“Trump knows if he has committed crimes, and if he has, he knows he is going to be caught – the special counsel is too good not to catch Donald Trump."
The White House has denied any collusion with the Russians in Trump’s election victory – and Trump has decried it as a “witch hunt”.
His supporters claim the probe is politically motivated and Trump has been called upon to use his executive powers to end the probe.
Mueller’s net continues to get bigger however as key members of Trump’s inner circle have been roped in.
Donald’s daughter Ivanka’s husband Jared Kushner has been interviewed in the probe.
Don Jr would be the person closest to Trump to fall to Mueller, and Lichtman believes he is bang-to-rights.
Trump took aim at Mueller once again this week with an explosion on Twitter, once again branding it a “witch hunt” helmed by “thugs” that was “absolutely nuts”.
The US President sacked the attorney general Sessions after the midterms, who he had often criticised over the probe.
His replacement Whitaker has previously brushed off claims of wrongdoing by Don Jr, saying “you would always take that meeting”.
And he is previously been openly critical of the Mueller probe, calling it a “mere witch hunt”.
He suggested widening the probe – which Mueller could – would be a “violation”.
Lichtman said he believes Trump will use Whitaker to squeeze the Mueller probe - but he does not believe the US President would outright fire the special counsel, but will attempt to quietly wind it down.
“I cannot imagine any other reason for putting in someone [like Matt Whitaker] who is so unqualified other than to deal with the Mueller investigation,” the professor said.
“There are many ways in which he can undermine the investigation without firing outright Mueller, which don’t think he will do.
“He can reduce funding, he turn down subpoenas, he can turn down indictments, and he can turn down the release of a final report.”
