"Is it conceivable that [Manafort] and Jerome Corsi, who is saying Mueller's people are pressuring him to lie, are telling the truth and the special counsel in their zeal to get the president may be going too far?" Giuliani told NBC.
Trump began his trio of tweets Tuesday morning by again labeling the probe of Russian meddling in the 2016 U.S. presidential election a "Phony Witch Hunt." The president complained that Mueller's team was "only looking at one side, not the other," appearing to refer to his former political opponent Hillary Clinton, who he has long claimed broke the law through her use of a private email server.
The White House did not immediately respond to CNBC's inquiries about Trump's tweets. The special counsel declined to comment.
On Monday night, Mueller accused Manafort of breaching the terms of his plea agreement by lying "on a variety of subject matters" to investigators.
The allegation, revealed in a filing in Washington, D.C., federal court, did not say what Manafort is specifically accused of lying about, but said that the government would "file a detailed sentencing submission to the Probation Department and the Court in advance of sentencing that sets forth the nature of the defendant's crimes and lies, including those after signing the plea agreement herein."
The filing also said the alleged breach relieves the special counsel of its own obligations under the plea agreement, which was reached on the eve of Manafort's second trial. Those obligations included agreeing to reduce Manafort's prison sentence "for acceptance of responsibility."
The charges lodged against Manafort related mostly to work he performed years before joining the Trump campaign, when he was working for a pro-Russia political party in Ukraine.
Trump has shown sympathy for targets in the Russia probe before. After Manafort was found guilty on eight criminal counts in a trial in Virginia brought on charges lodged by Mueller, Trump tweeted that he feels "very badly" for Manafort and his family.
Trump has also avoided a straight yes-or-no answer on the possibility of a pardon for Manafort in the past.
Trump's suggestion that Mueller is "ruining lives" of people for "refusing to lie" has been floated by other individuals targeted by the special counsel.
Corsi, one of the leading proponents of the false "birther" conspiracy theory which alleged that former President Barack Obama was not born in the U.S., said Monday that he was offered a plea deal on one count of perjury. But the former Infowars bureau chief, who also proliferated the much-criticized "Swift Boat" campaign against 2004 Democratic presidential frontrunner John Kerry, said he would "rather sit in prison and rot" than say he lied.
Corsi did not immediately respond to CNBC's questions about Trump's tweets.
Trump latched on to the birther conspiracy theory in 2011 and quickly became among the loudest public crusaders for the narrative, which has been widely condemned as racist. Trump finally acknowledged that Obama was born in the U.S. in September 2016, just before the 2016 election.
Meanwhile, former Trump campaign aide George Papadopoulos, the first person to be charged in Mueller's probe, was incarcerated in Wisconsin federal prison Monday. Papadopoulos pleaded guilty to lying to federal investigators in October 2017.