WASHINGTON — Republicans in control of Congress reacted with a collective shrug Tuesday to the revelation that top Trump administration national security officials had used a messaging app to chat about military operations, even as Democrats expressed outrage and called for an investigation and resignations.

One day after the existence of a group chat about airstrikes in Yemen — and the inclusion of a journalist in it — came to light, leading Republicans and most rankand-file GOP lawmakers refrained from criticizing the administration, though some suggested they might look into how the breach had occurred.

Sen. John Thune of South Dakota, the majority leader, told reporters that there were “errors in judgment” among the officials who took part in an encrypted group chat on the app Signal. He initially suggested it was up to the Trump administration to address them, but later appeared open to the possibility of the relevant Senate committees beginning their own inquiry.

“I suspect the Armed Services Committee may want to have some folks testify and have some of those questions answered,” he said during a news conference Tuesday afternoon. “What we want to do is make sure that something like that doesn’t happen again.”

Speaker Mike Johnson read directly from a White House press statement during a news conference on Capitol Hill  and rejected the notion of firing Michael Waltz, the national security adviser, who had set up the group chat and included Jeffrey Goldberg, the editor-in-chief of The Atlantic.

“He was born for the job. He is highly qualified,” Johnson told reporters. “The president said he has total confidence in him, and we do as well.”

It was the latest example of how the all-Republican Congress, which is ceding much of its power to an emboldened President Donald Trump at the start of his second term, has shown little appetite for exercising any oversight over the administration.

Trump, for his part, continued to attack The Atlantic and Goldberg, and sent mixed messages on whether the administration would change how it goes about sharing sensitive information going forward.

“We won’t be using it very much” in the future, Trump said of Signal. “That’s one of the prices you pay when you’re not sitting in the Situation Room with no phones on, which is always the best, frankly.”

Trump added, “If it was up to me everybody would be sitting in a room together. The room would have solid lead walls and a lead ceiling and lead floor.”

A few Republicans were more publicly critical.

Sen. Lindsey Graham, R-S.C., called the chat “a mistake” that could have led to grave consequences, even as he defended Waltz as “the right guy” for his job.

“We dodged a bullet,” Graham said. “I hope we understand what happened and never do it again.”

Asked whether he agreed with the White House’s denial that “war plans” had been discussed in the chat or that classified information had been shared, Graham said the Intelligence Committee should “take a look at that in a bipartisan way.”

Sen. Roger Wicker of Mississippi, the chair of the Armed Services Committee, said his panel would look into what had happened but provided no details.

“We are definitely concerned,” Wicker told reporters, adding that he and his colleagues on the committee were “considering our options.”

Democrats, on the other hand, were unbridled in their expressions of anger and outrage about the incident and said a serious inquiry was warranted.

Sen. Adam Schiff, D-Calif., said making the information in the text chain available to a civilian had put “the lives of pilots and the success of operations at risk.”

Rep. Gregory Meeks of New York, the top Democrat on the Foreign Affairs Committee, pressed his Republican counterpart to hold a hearing to investigate what he called “the most astonishing breach of our national security in recent history.”

Like many other Democrats, Meeks pointed to the incident — and Republicans’ refusal to condemn it — as an example of what he called hypocrisy by GOP lawmakers who have “regularly contrived security ‘scandals’ to attack their political opponents with years of nakedly partisan hearings and investigations.”

“Any Senate Republicans who was up in arms years ago about emails and unsecured servers should be outraged by the secretary of defense’s carelessness,” Sen. Chuck Schumer, D-N.Y., the minority leader, said during a speech on the floor.

He was referring to the furor surrounding the revelation that former Secretary of State Hillary Clinton had used a private email account and server.

A handful of Democratic lawmakers called on Pete Hegseth, the secretary of defense, to resign. Some added that Waltz should, as well.

“Hegseth needs to resign, and everyone on that text chain needs to go take some courses on how to deal with national security classified information,” Rep. Ted Lieu, D-Calif., said during a news conference Tuesday morning.

Democrats vented their ire about the situation during a hearing Tuesday morning with top intelligence chiefs, who repeatedly denied that any classified information had been included in the group chat and largely refused to engage with lawmakers about what had been discussed or how the breach had occurred.

Sen. Mark Warner of Virginia, the top Democrat on the panel, denounced the actions of the administration officials involved, warning that it pointed to much larger problems.

“I think this is one more example of sloppy, careless, incompetent behavior, particularly toward classified information,” Warner said during the hearing scheduled to discuss national security threats around the globe. “The Signal fiasco is not a one-off.”

But both inside and outside the hearing room, many Republican lawmakers downplayed the incident. Most conceded that a mistake had been made but said an investigation led by the White House looking into how Goldberg had been inadvertently added to the thread was sufficient oversight of the incident.

“I don’t think most Americans care one way or another,” Sen. John Kennedy, R-La., said of the mistake.

He rejected the idea that Congress should investigate, saying: “I think the administration will do it.”

Sen. Jon Osoff, D-Ga., lambasted CIA Director John Ratcliffe during Tuesday’s hearing.

“This is an embarrassment,” Ossoff said. “This is utterly unprofessional.

There’s been no apology. There has been no recognition of the gravity of this error.”