Image source, Getty Images

"Is he on our country's side?" asks Democrat Jackie Speier, after reading a tweet in which Trump posed the same question about the whistleblower.

"Do you believe the whistleblower is on our country's side?" the California congresswoman asks.

Maguire responds: "I believe that the whistleblower and all employees who come forward to the ICIG [Intelligence Community Inspector General] to raise concerns of fraud, waste and abuse are doing what they perceive to be the right thing for our country."

"Did the president of the United States ask you to find out the identity of the whistleblower?" Speier continues.

"Although I would not normally discuss my conversations with the president, I can say emphatically, no."

The BBC's Anthony Zurcher points out a rare bit of Republican criticism of Trump regarding his call with Ukrainian President Zelensky.

Ohio Republican Mike Turner says: "I want to say to the president: this is not OK. That conversation is not OK. And I think it's disappointing to the American public when they read the transcript."

Yes.

The Whistleblower Protection Act (WPA) states that federal employees are protected when they lawfully disclose information that they believe shows violations of laws or rules, gross mismanagement, waste of funds, abuse of authority or substantial dangers to the public.

It was strengthened in 2012 by Congress to further protect those who report fraud, waste and abuse.

An intelligence community-specific act - passed in 1998 - also states that as long as officials use legal means to raise complaints, they are protected from prosecution or firing.

Image source, Getty Images

"This whistleblower complaint is only the tip of an iceberg of corrupt, illegal and immoral behaviour by this president," says Vermont Senator and Democratic presidential candidate Bernie Sanders.

"What the House must do is thoroughly investigate Trump’s cover-up of this call and his other attempts to use government resources to help his re-election campaign.

"The public deserves to have full transparency regarding Trump's abuse of office."

Other 2020 candidates, like California Senator Kamala Harris, have also weighed in.

With Speaker Nancy Pelosi backing impeachment, the House of Representatives committees currently investigating the president will eventually share their findings with the House Judiciary Committee.

It would then be up to the Judiciary Committee to decide whether to draft articles of impeachment against Trump before a full House vote on the matter.

If impeachment passed the Democratic-controlled House, it would move to the Republican-controlled Senate.

Read more on how President Trump could be impeached here

Alabama Democrat Terri Sewell pushed Maguire on whether the handling of the report would prevent others from coming forward to report future wrongdoing.

"I want to know whether or not you see how problematic this will be," Sewell asks, "having a chilling effect" on members of the intelligence community "that you are sworn to represent and, ostensibly, protect".

Maguire responds: "Congresswoman, I think that's a fair assessment. I don't disagree with what you've said."

You can peruse the acting director of national security's complete opening statement to the House committee here, external.

When asked if he ever spoke to Trump about the whistleblower, Maguire refuses to go into his conversations with the president.

"Congressman, I'm the president's intelligence officer. I speak with him several times throughout the week.

"My conversations with the president, because I am the director of national intelligence, are privileged. And it would be inappropriate for me, and it would destroy my relationship with the president in intelligence matters, to divulge any of my conversations with the president of the United States."

An attorney for the whistleblower has confirmed that an online fundraising campaign has been started for the US intelligence officer who filed the report.

"The US intelligence officer who filed an urgent report of government misconduct needs your help," the account says.

"This brave individual took an oath to protect and defend our Constitution. We're working with the whistleblower and just launched a crowdfunding effort to pay the whistleblower’s legal fees.

"The whistleblower took a great personal risk to defend our democracy, and did not do this for politics or personal gain. We need to have the whistleblower’s back."

Here’s a quick look at the big points from the whistleblower’s complaint:

• Multiple officials said they witnessed the president use his 25 July call with Ukraine’s leader "to advance his personal interests" and pressure him to help Trump’s re-election bid
• All records of the phone call were locked down by senior White House staff in a computer system typically used for sensitive national security information only
• Trump’s personal lawyer repeatedly said he wanted to encourage Ukraine to look into the Biden issue
• US officials said that Ukrainian leadership felt a meeting between the two presidents would only happen if Ukraine would “play ball” about the investigations the White House sought
• The order to suspend aid to Ukraine initially came "directly from the president" and left some officials "unaware of a policy rationale"

Image source, AFP

"You're going be part of a charade of legal word games," says Republican Devin Nunes, warning that Democrats plan to twist Maguire's answers for political purposes.

He asks about the determination that the whistleblower's complaint was "credible".

Maguire answers that the complaint did not relate to matters under his statutory purview, because it relates to people not under his command.

"I believed that the situation we had and why we're here this morning is because this situation is unique and unprecedented," he repeats.

He shrugs when Nunes asks why other cases like this are not handled in public.

Image source, Alex Wong/Getty Images

In a tense back and forth, House Intelligence Committee Chairman Adam Schiff and Maguire sparred over why the intelligence chief sought advice from the White House before deciding to release the report.

Schiff questioned why Maguire went to the "the subject of the complaint" to ask whether it should be submitted to Congress.

"It just seemed prudent to check," Maguire responds, saying he sought the advice of White House counsel to determine if the report included information protected by presidential executive privilege.

"I did not go for a second opinion," Maguire says.

Maguire continues: "I believe everything in this matter is totally unprecedented."

After prodding from Schiff, Maguire adds that he believes the whistleblower acted in "good faith".

"I think the whistleblower did the right thing. I think he followed the law every step of the way."

BBC North America Correspondent Anthony Zurcher is tweeting his analysis from inside the Capitol Hill briefing room.

He points out so far that Maguire has not taken the bait when asked if there has been any presidential "wrongdoing".

Maguire also refuses to condemn the whistleblower as a "political hack" when given the opportunity by Democratic Chairman Adam Schiff. This is a reference to Republican concerns that the whistleblower is motivated by animus towards Trump.

"I think the whistleblower did the right thing," adds Maguire.

Image source, MARCUS TAPPAN/AFP/Getty Images

Joseph Maguire, 68, is a retired Navy Seal who during a 36-year career rose to become a three-star admiral and leader of the US Naval Special Warfare Command.

PerceIved as the safe, experienced choice for acting director of national security by the White House, Maguire reportedly did not want the role of spy chief - or the attendant political battles.

Maguire initially refused to share the whistleblower complaint with lawmakers, but dismissed US media reports suggesting he threatened to quit if the White House forced him to stonewall Congress.

"At no time have I considered resigning my position," Maguire said in a statement. "I have never quit anything in my life, and I am not going to start now."

Maguire says Trump's release of a summary of the call allowed him to release the complaint and the inspector general's letter.

The inspector general told him, he says, that the urgent matter required him to submit the report to Congress.

"Let me also discuss the issue of 'urgent concern'," he says.

"Urgent concern is a statutorily defined term. To be of urgent concern the allegations must, in addition to being classified, assert a flagrant serious problem, abuse or violation of law, and relate to the funding, administration, or operation of an intelligence activity within the responsibility of the director of national intelligence.

"However, this complaint concerns conduct by someone outside the intelligence community, unrelated to funding, administration, or operation of an intelligence activity under my supervision."

He said the complaint did not meet the statute, according to his consultations with the Department of Justice Office of Legal Counsel.

Maguire adds: "I am not familiar with any prior instances where a whistleblower complaint touched on such complicated and sensitive issue including executive privilege.

“I believe that this matter is unprecedented."

Image source, Win McNamee/Getty Image

In a statement on Thursday, White House press secretary Stephanie Grisham said "nothing has changed with the release of this complaint", deeming it a "collection of third-hand accounts of events and cobbled-together press clippings - all of which shows nothing improper".

She continued: "The President took the extraordinary and transparent steps of releasing the full, unredacted, and declassified transcript of his call with President Zelensky, which forms the heart of the complaint, as well as the complaint itself. That is because he has nothing to hide.

"The White House will continue to push back on the hysteria and false narratives being peddled by Democrats and many in the mainstream media."

Joseph Maguire, acting Director of National Intelligence, says in opening statement: "The American public expects us to keep them safe. The intelligence community cannot do that without this committee's support.

"Before we turn to the matter at hand, there are a few things I would like to say. I am not partisan and I am not political. I believe in a life of service and I am honoured to be a public servant."

He says he has served in uniform under eight presidents and taken his oath 11 times.