A spokeswoman for McCabe did not provide comment for this story.
"It's shocking that the FBI would open up an obstruction case for the President exercising his authority under Article II," said the President's attorney Rudy Giuliani.
Prior to Comey's firing, top FBI officials had discussed opening an obstruction investigation based on the President saying to Comey, "I hope you can let this go" when discussing Flynn. That episode was later described in memos Comey wrote following the February meeting that the former FBI director would leak soon after his firing.
Comey's attorney did not comment for this story, but pointed to Comey's 2017 testimony to the Senate Intelligence Committee.
Comey, however, hinted at the discussion in his book.
"We resolved to figure out down the road what to do with the president's request and its implications as our investigation progressed," he wrote.
Then, on May 9, Comey was fired.
The subsequent meetings led by Rosenstein and McCabe were held soon after the White House made clear that Rosenstein's memo addressing concerns about Comey's conduct during the Hillary Clinton probe was central to the President's decision. One of the sources likened it to "spitballing" about potential steps in the mold of "What are the options. What makes sense. What doesn't?"
Trump's ire for obstruction inquiry
One source said there were "different conversations at different times with different people." The President then raised the stakes, telling NBC News in an interview that he fired Comey because of the "Russia thing."
Rosenstein's original public announcement appointing the special counsel did not specifically reference the obstruction issue, only "the previously-confirmed FBI investigation of Russian government efforts to influence the 2016 presidential election and related matters." But the order setting up the special counsel did include the legal code that includes investigating matters related to obstruction.
Rosenstein has been under constant fire from Trump and a frequent target of the President's tweets, and he was prepared to be fired after his comments about wearing a wire and the 25th Amendment were reported. He survived at the Justice Department but was passed over as acting attorney general for Jeff Sessions' chief of staff Matt Whitaker, who was seen as a loyalist to Trump and has publicly criticized the special counsel's investigation.
Both McCabe and Rosenstein have felt the withering criticism of the President. Just last week, Trump tweeted out a picture of Rosenstein in prison. Asked why he did that in an interview with The New York Post, Trump responded, "He never should have picked a special counsel."
This week, Rosenstein joked during a speech to "let the President know that his favorite deputy attorney general was here."
Trump has submitted written answers to Mueller's team about potential collusion between members of Trump's team and Russian officials, but he has not answered questions from the special counsel related to obstruction. It's still not clear whether Mueller will try to seek additional written testimony or an in-person interview from Trump related to the obstruction investigation. The President's lawyers have signaled they won't answer questions on obstruction because the time period falls under executive privilege.
The push for a special counsel
In the days immediately after Comey was fired, McCabe pushed for the appointment of a special counsel but Rosenstein seemed hesitant, despite many calls to do so.
McCabe and Rosenstein later met with the full "Gang of Eight," the Republican and Democratic congressional leaders and intelligence committee heads, the day Mueller was appointed.
Separately, Comey was orchestrating his own campaign to create public outcry for a special counsel. The former FBI director had a key memo about his interactions with Trump leaked to The New York Times, which published an article that Trump had asked Comey to go easy on Flynn on May 16. Mueller was appointed the next day.
It is not clear why the FBI first moved to open a case just before the appointment of a special counsel. However, the investigation of the President could have been seen as an impetus for having an independent team investigate given the sensitivities. At the time, those pushing for special counsel were focused on protecting the Russia investigation from further efforts by Trump to curtail it.