Questions about President Trump's firing of James Comey from the FBI dominated the Senate Intelligence Committee's hearing Thursday, and prompted senators to ask questions about how the bureau is continuing with its investigation into Russian activity in the 2016 elections without Comey there.

Here are five key takeaways from his testimony.

McCabe believes the FBI has "adequate resources" to conduct the Russia probe

McCabe said he believes the FBI has "adequate resources" for its probe into possible Trump campaign relations with Russia during the election.

"If you're referring to the Russia investigation, I do," McCabe said. "I believe we have the adequate resources to do it, and I know that we have resourced that investigation adequately."

His comments undermine the theory that Comey was fired just days after he asked the Justice Department for more funding and personnel for the investigation into Russia's meddling in the U.S. election. The New York Times and others reported that anonymous sources said Comey had just asked for more resources, and Democrats seized on those reports as evidence that Trump fired Comey to hinder the Russia probe.

Comey's firing has not slowed down Russia probe

McCabe said Trump's firing of Comey has not measurably slowed down the bureau's investigation into Russian meddling in the 2016 elections.

McCabe was asked by Sen. Marco Rubio, R-Fla., whether Comey's dismissal has hurt the FBI's investigation in any way.

"As you know, senator, the work of the men and women of the FBI continues despite any changes in circumstance, any decisions," McCabe said. "So there has been no effort to impede our investigation to date. Simply put, sir, you cannot stop the men and women of the FBI from doing the right thing, protecting the American people, and upholding the Constitution."

McCabe vowed not to give Trump updates on the status Russia investigation

McCabe promised not to give Trump updates on the status of the bureau's investigation into Russia's meddling in the 2016 election, after Trump indicated Comey provided him with these sorts of updates.

Sen. Ron Wyden, D-Ore., asked if it would have been wrong for Comey to give Trump that kind of information, and McCabe had no comment. But when Wyden asked if he would refrain from providing this kind of information to the president, McCabe answered, "I will."

No comment on whether Comey told Trump he is not being investigated

McCabe wouldn't confirm whether Comey told Trump he is not under federal investigation.

"Did you ever hear Director Comey tell the president he was not the subject of an investigation?" asked North Carolina Sen. Richard Burr, the chairman of the Intelligence Committee.

"I can't comment on any conversations the director may have had with the president," McCabe said.

In firing Comey, Trump wrote in a letter Tuesday: "I greatly appreciate you informing me, on three separate occasions, that I am not under investigation."

Comey had support of FBI's rank and file

McCabe also dismissed the notion that Comey no longer had the support of the rank and file of the FBI, something White House spokeswoman Sarah Sanders asserted Wednesday.

"No, sir, that is not accurate," McCabe said.

"I can tell you that I hold Director Comey in the absolute highest regard," McCabe said. "I have the highest respect for his considerable abilities in his integrity and it has been the greatest privilege and honor my professional life to work with him. I can tell you also that Director Comey enjoyed broad support within the FBI. And still does to this day."