Mrs Clinton's supporters cried foul when it emerged that the Trump election team was also under investigation by the FBI, but Mr Comey never divulged that until a long time after the election.
"Director Comey enjoyed broad support within the Federal Bureau of Investigation and still does to this day", McCabe said, saying he holds Comey in the "absolute highest regard".
In a series of early morning tweets, Trump assailed critics and the media over their response to Comey's ouster, and threatened to cancel daily news briefings at the White House.
"I said, 'If it's possible, would you let me know, am I under investigation?' He said you are not under investigation", Trump said in an interview Thursday with NBC News.
The US President said the dinner with Mr Comey was at the White House and Mr Comey wanted to discuss staying on as Federal Bureau of Investigation chief. Trump told NBC he had planned to fire Comey all along, regardless of whether top Justice Department officials recommended the stunning step.
"We've talked to - again, several legal scholars have weighed in on this and said there was nothing wrong with the President asking that question", she said, without naming names.
The White House initially cited a Justice Department memo criticizing Comey's handling of last year's investigation into Hillary Clinton's emails as the impetus for Trump's decision.
He said in an NBC News interview on Thursday that Mr Comey told him once over dinner and twice by telephone that he is not under investigation.
McCabe also pointed out the remarkable nature of Trump's version of his conversations with Comey.
The White House has drawn criticism for the timing of Comey's firing, which occurred as the Federal Bureau of Investigation continued to investigate Russian interference in the 2016 election and possible connections with the Trump campaign.
In firing Mr Comey, Mr Trump said he knew he ran the risk he would "confuse people" and "lengthen out the investigation" into ties to Russian Federation.
Mr Trump's explanation of why he fired Mr Comey also ran counter to previous administration explanations of the dismissal.
"I can not defend the Director's handling of the conclusion of the investigation of Secretary Clinton's emails, and I do not understand his refusal to accept the almost universal judgment that he was mistaken", Mr Rosenstein goes on to say.
Moscow has denied interference in the election, and the Trump administration denies allegations of collusion with Russian Federation.
"Again, the story that there was collusion between the Russians & Trump campaign was fabricated by Dems as an excuse for losing the election", he wrote.