Defense Secretary Jim Mattis has avoided taking a visible role in the Trump administration since it took office last year, avoiding cameras and cable news shows.

However, he stepped into the spotlight last week when he backed up the president’s decision to sign a massive spending bill.

On Friday, an uneasy President Trump addressed the nation, announcing he had signed the $1.3 trillion bill that many in his base found distasteful.

Flanked by Mattis and Vice President Michael Pence on one side, and Commerce Secretary Wilbur Ross and Homeland Security Secretary Kirstjen Nielson on the other, Trump said he would sign it because it would help rebuild the military.

The bill included $700 billion in defense spending for 2018—the largest budget the Pentagon has ever seen and a 10 percent increase from 2017—with even more for 2019. Behind the scenes, Mattis had fought hard for those top lines.

Mattis then did something he rarely does—make a live on-camera statement. The first to speak after Trump, he hailed the bill, effectively backing up the president, and even using superlatives reminiscent of Trump.

“As the president noted, today we received the largest military budget in history, reversing many years of decline and unpredictable funding. And together we are going to make our military stronger than ever,” he said.

Standing in front of the omnibus spending bill, Defense Secretary Mattis discussed the favorable expenditures that the massive spending bills entails for the military. President Trump reluctantly signed the bill in order to secure a necessary increase in military spending. pic.twitter.com/2WCADeTMTp — FOX Business (@FoxBusiness) March 24, 2018

“Thank you very much, General,” Trump said. Although it is common to call a retired general officer “General,” to some observers, it seemed like the president was leaning on Mattis as a prop.

Even before the announcement, there were reports that said Trump was considering vetoing the bill, but Mattis had warned him against flatlining defense spending.

That evening, the White House announced its transgender policy, which would ban most transgender individuals from serving. Many had expected Mattis to oppose Trump’s ban on transgender troops, but the new policy was based on his recommendations.

And the last time Mattis appeared at a formal on-camera press conference with reporters, it was at the White House—not the Pentagon—to urge Congress to pass a budget.

A senior defense official told Breitbart News in December that Mattis was unlike his predecessors in that he was completely apolitical, likely due to his background in the military.

But his recent appearance Friday raised questions over his seemingly growing role inside the administration, prompting no fewer than five profile pieces by Monday.

“He’ll be the last man standing,” Mackenzie Eaglen, a defense analyst with the American Enterprise Institute, told Bloomberg News in one of those profiles. “He is the most powerful Cabinet member and knows it.”

Some defense experts disagree that Mattis is becoming more of a political player, and say it is his role as defense secretary to advocate for defense spending.

“Interests kind of coincided,” said Lt. Gen. (Ret.) Tom Spoehr, director of Heritage’s Center for National Defense. “He has heard from all the services and all of his people about how they need money and they need it now.”

Rebeccah Heinrichs, senior fellow at the Hudson Institute, agreed. “If the secretary of Defense doesn’t advocate hard for the defense spending bill, it’s dead in the water.”

But the episode illustrated Mattis’ ability to walk Trump back from a veto threat, even on something that would be unpopular with his base.

“While the president seemed like he really didn’t want to sign the omnibus bill for a variety of reasons, I imagine Mattis made a strong argument for his Defense priorities in a way that resonated with Trump, and rebuilding the military is a real priority and a campaign promise of his.” Heinrichs said.

A large part of Mattis’ clout comes from his popularity, on the right and the left. A Politico poll conducted earlier this month showed that Mattis is the most approved-of member of Trump’s cabinet.

“He starts with a fair amount of good will in the bank. He’s banked a lot of integrity and good will over the years, based on his service, the fact that he has not drawn attention to himself,” Spoehr said.

He has also remained scandal free, unlike some of his former colleagues. His perceived lack of political motivation has also helped. To form his recommendations on the transgender policy, he appointed a panel of experts to study the issue.

The omnibus episode also exhibited a skill that has given Mattis staying power in the administration—putting forth his views in a way that did not run afoul of the president, unlike some of his peers.

“He makes his views privately known to the president, that typically doesn’t leak out,” Spoehr said. “And the president makes the decision and you wouldn’t be able to tell by watching Secretary Mattis whether it was his recommendation or not, because he implements, executes, and supports it.”

Mattis continued that deftness when asked about his reaction to the president’s veto threat during an impromptu off-camera gathering with reporters on Tuesday.

“The president rightly looks into every assumption, challenges every assumption, challenges everything that’s going on. He was elected to do that. He’s not elected to be a potted plant,” he said. “This is the normal heave and ho of a democracy in action.”

Heinrichs said Mattis understands that he works for the president “and not the other way around.”

“Trump isn’t the only one who resents feeling ‘managed.’ Ask any member of Congress or executive and he or she will tell you the same thing. And a staffer who gets out ahead of his boss or tries to undermine that boss’s priorities won’t last long, at least most don’t,” she said.

Trump was reportedly annoyed by his outgoing National Security Adviser H.R. McMaster, who would try to slip in or take out certain phrases from his prepared speeches, such as the words “radical Islamic terrorism.”

There were other clear differences between Mattis and McMaster’s approach. Mattis is quiet and circumspect, whereas McMaster likes to talk, if not lecture. McMaster was also prone to emotion.

During a meeting last year at the Pentagon, McMaster got into a heated exchange with then-White House chief strategist Stephen K. Bannon. Mattis gently placed his hand on McMaster to calm him down, a source told Breitbart News last year. At the time, a defense official vigorously denied the account.

Some international officials also saw a difference. When asked recently by Breitbart News about Mattis and McMaster, a senior official of a partner nation responded, “Mattis is a very mature man.” McMaster, the official said, “needs to spend more time with us.”

Mattis’ support of the president has not appeared to hurt him with the left, as it had hurt McMaster every time he took the podium in defense of the president.

Although some reacted with disappointment to Mattis’ transgender policy recommendations, criticism against him was mostly muted. Others blamed Vice President Mike Pence for the policy instead.

Mattis even offered a few words of support when asked about it during a photo opportunity with the Indonesian defense minister on Monday. “We are out to build the most lethal service,” he said.

Still, many continue to perceive Mattis as their only hope to moderate Trump, and fretted that incoming National Security Adviser Amb. John Bolton could pose a challenge to him.

The New York Times Magazine ran a piece on Mattis Monday entitled: “Last Man Standing: Jim Mattis may be the last voice of caution in an increasingly volatile administration. Can he hold the line?”

Mattis on Tuesday vigorously dismissed the idea that there would be any problem working with Bolton, and said the two were planning on meeting at the Pentagon soon.

“We’re going to sit down together and I look forward to working with him. No reservations, no concerns at all. Last time I checked he’s an American. I can work with an American, OK? So I’m not the least bit concerned,” he said.

Heinrichs dismissed the narrative that Mattis is trying to moderate Trump.

“I think the common perception in the media that Mattis opposes a lot of what Trump is doing or wants to do abroad is likely untrue. It’s projection,” she said.

“I think more in the media should consider the possibility that they’re the ones being managed by the secretary.”