Gingrich told The Associated Press in an interview this week that his feelings about him began to change after Comey testified to a Senate panel that he had leaked his personal memos in order to trigger the appointment of a special counsel.
The message was the first explicit concession by the president that Robert Mueller, the special counsel for the Russian Federation inquiry, had begun examining whether Trump's firing of Comey last month was an attempt to obstruct the investigation.
The president has denied that he has any nefarious ties to Russian Federation and has also disputed that he's attempted to block the investigation into his campaign's possible role in Russia's election-related hacking. They hint that Trump could still try to remove Mueller, a possibility that must be taken more seriously now that Trump is a target. "Witch Hunt", Trump said in a Twitter message.
Trump kept up his criticism of the investigations, writing on Twitter, "After 7 months of investigations & committee hearings about my 'collusion with the Russians, ' nobody has been able to show any proof".
That appeared to be the first public confirmation that Trump is being investigated for obstruction of justice - and was a digital salvo aimed at Deputy Attorney General Rod Rosenstein, who wrote a memo criticizing Comey.
After Comey's firing, Rosenstein appointed Mueller to lead an independent investigation on matters involving Russia's alleged meddling and related matters.
The transition official spoke on condition of anonymity because the person was not authorized to discuss post-election decisions publicly.
But later, in an interview with Lester Holt, the president said he had already made up his mind. Though some in the White House have preached caution, fearing a repeat of the firestorm over Comey's firing, many in Trump's orbit - including his son Donald Trump Jr. and adviser Newt Gingrich - have deemed Mueller biased and worthy of dismissal.
Mr. Trump's lawyer has accused the Federal Bureau of Investigation of leaking material.
The memo that Mr. Comey drafted in which he detailed ways in which the president might have acted improperly to influence an ongoing investigation is confirmed to exist, but it has yet to be turned over the Congress.
He has decided - after consulting with a small circle of advisers in multiple meetings over the last few days - that "this is a political fight and he's going to fight it", the official said.
A second source also told Fox News that Trump was not in fact admitting to being the subject of an active investigation, but rather was referencing content found in a recent article in The Washington Post.
Meanwhile, former House Speaker Newt Gingrich slammed Mueller for reportedly launching investigation against Trump.
Trump was set to escape the Washington pressure cooker on Saturday. Comey told the Senate Intelligence Committee that he chose to document his communications with Trump for fear that the president would subsequently misrepresent them. Comey was sacked by the president on May 9 while he was overseeing the investigation into potential Russian interference into last year's election and potential collusion with the Trump presidential campaign.