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After unrelenting questions about alleged Russian meddling in the 2016 election, President Donald Trump said in an exclusive interview with NBC News' Lester Holt that "we're fighting hard" when asked about his credibility being called into question.

"Do you feel like you're fighting for your legitimacy sometimes?" Holt asked during a 31-minute interview Thursday at the White House, a segment of which aired Friday on TODAY.

"Well, we're fighting hard," Trump said.

"That your legitimacy is under attack?" Holt asked.

"Well, we have a very divided country," Trump added. "I mean, the Republicans are very, very much behind me. They love what we're doing on health care. Obamacare is dead. It's a disaster."

Holt had also asked whether Trump still has pinch-me moments about occupying the White House — as evidenced when he said during an executive order-signing event in the Rose Garden last week: "Hey, I'm president. Can you believe it?"

"I think when you become president, it's very special when you're in the White House. It's very special, and I had all of my Republican friends, who frankly have been in politics all their lives and have done a great job — but I did," Trump said. "I looked around and I said, 'Sorry folks, can you believe it's me?'"

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But the real estate mogul-turned-president's first few months in the White House have been dogged by questions over his campaign's ties to Russia, and now, the firing of FBI Director James Comey.

Related: President Asked Comey If He Was Under Investigation

There have been shifting stories from the administration about why Trump decided Tuesday to remove Comey, who had been the FBI chief since President Barack Obama appointed him in 2013. Comey was investigating Russia's alleged hacking against Democrats during the election.

Trump reiterated to Holt that he had been planning to fire Comey even before he received Deputy Attorney General Rod Rosenstein's recommendation to do so.

"He made a recommendation, but regardless of [the] recommendation, I was going to fire Comey," Trump said.

"In fact, when I decided to just do it, I said to myself, I said, 'You know, this Russia thing with Trump and Russia is a made up story. It's an excuse by the Democrats for having lost an election that they should have won," he added.

That contradicted White House officials, including Vice President Mike Pence, who had said Comey was fired on Rosenstein's recommendation. Aides also told reporters over the past two days that the Russia investigation had nothing to do with Comey's firing, and was a result of the FBI director's handling of the probe into Democratic challenger Hillary Clinton's use of a private email server while secretary of state.

Trump in his interview also branded Comey as a "showboat," who was "not the right guy" for the job.

Holt asked Trump about the termination letter he sent to Comey in which he wrote, "I greatly appreciate you informing me on three separate occasions that I am not under investigation."

Related: Fact Checking Donald Trump’s Interview With NBC’s Lester Holt

When asked what those three occasions were, Trump said they occurred once over dinner and twice over the phone — and that Comey explicitly told him he was not the focus of the investigation, according to Trump.

Several legal experts have told NBC News that the president's decision to ask whether he was under investigation and be told by the FBI that he is not is improper because it raises the issue of potential intimidation and conflicts of interest.

But Trump told Holt that he wants an investigation into any Russian interference to move forward with a new FBI director, who has yet to be named.

"As far as I'm concerned, I want that thing to be absolutely done properly," he said, adding, "I might even lengthen out the investigation, but I have to do the right thing for the American people. (Comey's) the wrong man for that position."