GEOFF BENNETT: After a weekend of new revelations and headlines, the White House today faced more questions about Secretary of Defense Pete Hegseth.

And at least one Republican lawmaker is now calling on him to resign.

Some of this is related to Hegseth's use of the Signal messaging app to text operational details of military action.

But our Lisa Desjardins joins us now to report that is not the only issue here.

So, Lisa, that sets us up well.

Take us through what has transpired in recent days.

LISA DESJARDINS: A lot to say, so I want to be very clear.

Let's start with last Friday.

Now, on that day, that is when four top Pentagon staffers in Hegseth's inner circle were suddenly out.

That includes the top staffer, his chief of staff there, who resigned from that job, as Politico reported, and three others who were just below that chief of staff level.

All have known him a long time, all accused in the media of leaking and were fired.

Next, Sunday, The New York Times reported and PBS has confirmed that Hegseth used a second Signal chat in which he messaged sensitive information about that Yemen attack.

And, per our source, he included in that chat his wife.

That includes obviously a major breach of security and secrecy protocols.

Then, also yesterday, Hegseth's former top communications person, his chief spokesperson, John Ullyot, wrote an op-ed in Politico saying he needed to go.

Now, if you read that op-ed, you saw that Ullyot wrote that: "The Pentagon is no longer focused on war fighting, but on endless drama and chaos."

Ullyot is a Marine veteran, but he's also a D.C. communications, so him writing that op-ed is highly unusual and significant.

GEOFF BENNETT: What are the White House and Hegseth saying today in response to all of this?

LISA DESJARDINS: They are strongly defending their defense chief.

They have said that -- in fact, Hegseth himself spoke this morning at the White House Easter egg roll.

PETE HEGSETH, U.S. Defense Secretary: This is what the media does.

They take anonymous sources from disgruntled former employees, and then they try to slash and burn people and ruin their reputations.

It's not going to work with me, because we're changing the Defense Department, putting the Pentagon back in the hands of war fighters.

And anonymous smears from disgruntled former employees on old news doesn't matter.

LISA DESJARDINS: But it was not anonymous, as we just reported.

His former own communications chief and three others have raised questions about this.

President Trump, however, said firmly today that he has great confidence.

And I also want to point out this from the White House press secretary, who made this statement about Hegseth today: KAROLINE LEAVITT, White House Press Secretary: The president stands strongly behind Secretary Hegseth, who is doing a phenomenal job leading the Pentagon.

And this is what happens when the entire Pentagon is working against you and working against the monumental change that you are trying to implement.

LISA DESJARDINS: The entire Pentagon working against you, obviously, that's hyperbole in one sense, but it also is an incredible statement from the White House about where they see the problem and potentially who they see the enemy is.

They're standing behind Hegseth, but they're pointing out as the problem being the entire rest of the Pentagon.

GEOFF BENNETT: And what's the impact of all of this, based on your reporting?

LISA DESJARDINS: Right, a lot of impact.

First, there's the job itself.

Scores of Democrats are calling for Hegseth to resign, and that one Republican is Congressman Don Bacon of Nebraska, who says it's time for him to go.

Behind the scenes, I am told by those at the Capitol with knowledge that they think the next 24 to 48 hours are the critical zone here.

Now, of course, President Trump is in the driver's seat here, regardless.

But those in the national security sector say there are much greater impacts potentially, that this is a signal to our adversaries that perhaps it's an opportunity for them to ramp up counterintelligence, that there's problems here in the U.S. military sector that they could take advantage of.

And, also, there's another issue here that it sends a message potentially to this military -- the military, where command and conduct are everything.

We spoke to one expert who's worked in the Defense Department, Kori Schake from the American Enterprise Institute.

KORI SCHAKE, Former National Security Council Staff Director: If anybody wearing an American military uniform did what Secretary Hegseth has done, they would be drummed out of the service.

They'd be lucky if they weren't court-martialed and sent to prison for it.

And so the lack of respect for the rules of the institution and the culture of the institution is corrosive.

LISA DESJARDINS: There's a debate over whether the Signal chat was worthy of a court-martial, but everyone I spoke to today said, yes, there would be severe consequences by anyone else in the military.

Now, Schake also said, no agency responds more quickly to political directives than the Pentagon.

So, blaming the Pentagon for being unresponsive does not really click with her.

One more thing for the staff turnover, one former U.S. defense official that I spoke with told me that, when there's uncertainty at the top of the Pentagon, it could cascade.

So the issue now for Hegseth is whether he can quell all of this uncertainty, all of this seeming kind of turmoil around him in time to save his job and also to make sure there's no problems at the Pentagon.

GEOFF BENNETT: Lisa Desjardins, thank you so much for this reporting.

We appreciate it.

LISA DESJARDINS: You're welcome.