The president's people are now lining up to testify against him. I asked a former Trump aide and a Watergate prosecutor why

One week after he took the oath of office to become the 45th President of the United States, Donald Trump famously told then-FBI Director James Comey: "I need loyalty. I expect loyalty.”

Since assuming the presidency, Trump has expressed that need by demanding nothing short of total obedience from those serving under him, often enforcing that demand with ruthlessness.

Republican officeholders who dared criticize him have found themselves subject to blistering attacks at best, and at worst have found themselves looking for employment in the private sector. And ever since he successfully hounded Republican dissenters — even GOP stalwarts like former Senators Jeff Flake and Bob Corker, or former South Carolina Governor and Congressman Mark Sanford — out of office for apparently insufficient loyalty, Republicans in Congress have generally given up calling Trump out for his increasingly bizarre behavior.

But a gigantic crack has appeared in the president’s facade of invincibility this week. A succession of witnesses parading in and out of the House Intelligence Committee's secure rooms has become a sure sign that after 998 days in office, Trump’s ability to cow his executive branch subordinates into silence appears to have reached its limit.

The first sign of this came on Friday, when former US Ambassador to Ukraine Marie Yovanovitch told members of Congress that Trump had ordered her recall in response to "unfounded and false claims by people with clearly questionable motives” — namely Trump’s personal attorney Rudy Giuliani and two of his now-indicted associates.

Yovanovitch, a career foreign service officer, made her appearance on Capitol Hill just four days after White House Counsel Pat Cipollone released a dramatically worded letter to House Speaker Nancy Pelosi and her team, in which he declared that Trump "[could not] permit his administration to participate" in the House's impeachment inquiry.

In the days since, it has become clear that an increasing number of current and former members of his administration no longer seem to care what the White House Counsel thinks.

On Monday, Fiona Hill, formerly Trump's top Russia expert, told impeachment investigators that Trump and Giuliani had bypassed career diplomats to run a shadow foreign policy meant to personally benefit Trump. While White House lawyers tried to insist that she refrain from revealing details of communications between Trump, diplomats, and foreign leaders, her attorney responded to the White House's demands by noting that executive privilege "disappears altogether when there is any reason to believe government misconduct occurred."

More administration officials are expected to give testimony in the coming days. Today, it's Deputy Assistant Secretary of State for European and Eurasian Affairs George Kent who will speak to the House Intelligence, Foreign Affairs and Oversight committee members and staff.

On Wednesday, they will hear testimony from Michael McKinley, the former senior adviser to Secretary of State Mike Pompeo, who resigned last week over his dismay at Pompeo’s failure to support career personnel who have been caught up in the Ukraine controversy.

And on Friday, Deputy Assistant Secretary of Defense Laura Cooper is expected to appear in yet another closed session, which, according to House Intelligence Committee Chairman Adam Schiff, is meant to keep Trump's allies from trying to get their stories straight based on public testimony.

Even Ambassador to the European Union Gordon Sondland, who Trump previously blocked from appearing, is set to finally testify on Thursday.

When I asked former Trump campaign aide Sam Nunberg why he thought people were finally coming forward, he told me he wasn't convinced that it had anything to do with weaknesses on Trump's part, stressing that his loyal supporters in Congress would continue to make objections based on the House's failure to hold a vote on its impeachment probe. Nunberg also predicted that the president's defense would focus on the fact that the military aid he is accused of holding up for political purposes was eventually released, but admitted that the number of people coming forward with information isn't a good sign.

"You can get into whether or not he was trying to hold up the aid, but at the end of the day the aid was given," he said. "With that said, people are showing up and in a perfect world, it would be better for the president's defense if they didn't.”

One of the House Democrats who has been involved in the investigation, Rep. Jamie Raskin, attributed the number of cooperative administration witnesses to the level of patriotism commonly found in the US civil service, and to the overall weakness of Trump's privilege claims.

"I think that witnesses are acting out of a sense of patriotic and legal duty," Raskin said in a text message. "They understand that they are contributing to an essential moment in our history and they don't see any reason to face charges of contempt of Congress for a president who seems to lose cases in court on a daily basis."

That these career professionals and experts aren't bowing to the White House's demands also comes as no surprise to former Watergate special prosecutor Nick Akerman.

"The fact is, these people aren't beholden to Donald Trump," Akerman told me. "They've been subpoenaed and that overrides Trump's counsel's statement. They have to obey the subpoena."

Akerman explained that in his experience, career professionals have a low tolerance for shadiness: ”When Nixon tried to get the IRS to audit people on his enemies list, he got stymied because people in the civil service wouldn't go along with the craziness and illegality.”

Akerman also suggested that the House's impeachment probe has given those officials who might not have been able to speak out before a chance to do so within a legal framework — particularly if they, like Hill, have lawyers to advise them that the White House Counsel's arguments against cooperation are bunk.

"They know that this is their opportunity to let it all hang out," he said. "That letter has zero legal force. You don't have to be a super lawyer to understand that."

Moreover, Akerman predicted that more Trump administration officials — current and former — would choose to speak out rather than stay silent and risk legal peril for themselves.

"If you compare it to Watergate, Nixon had real loyalists who'd lay and die in front of a steamroller for him. Other than maybe his daughter and son-in-law, there aren't a lot of people I'd put money on to take a bullet for [Trump],” he said.

It appears that the only person willing to be the proverbial Secret Service agent to House Democrats' John Hinckley Jr. so far is Rudy Giuliani, who told ABC News that he won't be complying with a subpoena for documents pertaining to the off-the-books errands he has been running for Trump in Ukraine.

“If they enforce it then we will see what happens," he said.