IN PLUNGING INTO A MIDEAST CONFLICT, TRUMP GAMBLES HIS PRESIDENCY

Six American service members were killed, and U.S. military jets were shot out of the sky. Investors are bracing for market turmoil, fearing prolonged disruption to oil supplies. President Trump says the military campaign against Iran could extend for weeks, and Secretary of State Marco Rubio said Monday that “the hardest hits are yet to come from the U.S. military.”

With his decision Friday to authorize war against Iran, Mr. Trump is taking the biggest gamble of his presidency, risking the lives of American troops, more deaths and instability in the world’s most volatile region, and his own political standing.

Mr. Trump, facing declining approval ratings and staring down the possibility that Republicans will lose control of Congress in the midterms, plunged the United States into what is shaping up to be its most expansive military conflict since the 2003 invasion of Iraq.

In just over a year since taking office, Mr. Trump has authorized military action in seven nations, even after he repeatedly promised American voters that he would end, not start, wars. During his inaugural address, he said his “proudest legacy will be that of a peacemaker.”

Even as he has struggled to provide a clear endgame for the military campaign, Mr. Trump has portrayed the operation as a resounding success. He has acknowledged the U.S. casualties as a cost of war but has spent more effort on boasting about the killing of Ayatollah Ali Khamenei, Iran’s supreme leader, the destruction of military targets across the country, and his commitment to keeping Iran from ever being able to produce a nuclear weapon.

But interventions in the Middle East have bedeviled generations of American presidents. Conflicts there scarred the legacies of Presidents George W. Bush, who led the country into lengthy wars in Iraq and Afghanistan that came to be deeply unpopular, and Jimmy Carter, whose failed operation in 1980 to rescue American hostages in Iran has been top of mind for Mr. Trump.

Now it is Mr. Trump who is orchestrating a rapidly expanding military effort in a region whose history and religious and factional politics make it an especially complex battleground.

“Presidents are reluctant to engage in these situations unless we are provoked, attacked directly,” said Barbara Perry, a presidential historian at the University of Virginia’s Miller Center. “Then there is usually a rally around the flag effect. You’re not going to have that now.”

While a handful of prominent voices in his movement have publicly denounced the decision to go to war, Mr. Trump’s base appears to be standing by him, for now. Still, some of the president’s allies privately worry that there is little political upside to the attacks on Iran and huge downsides, particularly the loss of U.S. troops and rising cost of oil.

Democrats have seized on the strikes to paint Mr. Trump as more focused in foreign intervention than addressing Americans’ economic worries at home.

“Trump sold voters on a ‘pro-peace’ vision of himself as an America First candidate, yet in under 13 months, he has ordered strikes on seven foreign nations and plunged our country into more open-ended conflict using taxpayer dollars,” Ken Martin, the chair of the Democratic National Committee, said in a statement. “While he’s distracted by foreign conflicts and shiny ballrooms, Trump has failed to deliver on his promise to bring costs down for working families, who are paying more every day because of Trump’s actions.”

Early polling after the attacks show most voters are not in favor of them. A CNN poll found 59 percent of Americans disapprove of Mr. Trump’s decision to launch strikes against Iran, and Reuters-Ipsos poll found that only 27 percent of Americans approve of the military campaign.

Should the conflict go badly or Iran descend into turmoil, it could leave Republican candidates in the midterm elections faced with difficult choices about whether to distance themselves from Mr. Trump on the issue.

And the war poses challenging questions for those looking to lead the party in the future, complicating the “America First” ideology at the core of the movement.

“This is not what we thought MAGA was supposed to be,” wrote former Representative Marjorie Taylor Greene, the Georgia Republican who broke with Mr. Trump last year and then resigned from Congress, in a social media post. “Shame!”

In a subsequent post, Ms. Greene called the Trump administration a “bunch of sick liars,” punctuating it with an expletive. “We voted for America First and ZERO wars,” she wrote.

Still, Matthew Boyle, the Washington bureau chief of Breitbart News, said he received almost no questions or comments from listeners during his weekly three-hour radio program on Saturday, hours after the strikes. The program, he said, provides a good window into the issues animating Mr. Trump’s base.

Mr. Boyle said he discussed the war extensively and played Mr. Trump’s early morning video announcing the attacks. Listeners, he said, were more interested in other topics. He said that was a stark contrast to the program he hosted after the United States captured Nicolás Maduro, the president of Venezuela, a topic many listeners wanted to discuss.

This time, he said listeners were much more interested in the economy, immigration and crime. But he warned that could change depending on how the operation unfolds.

“It all comes down to the results,” he said.

Sensing some of the fractures among Mr. Trump’s base, the White House on Monday started to respond directly to criticism on the right. Matt Walsh, a conservative commentator and a prominent voice among Mr. Trump’s supporters, posted on social media that Mr. Trump’s messaging on the U.S. objectives in Iran “is, to put it mildly, confused.”

Karoline Leavitt, the White House press secretary, responded to Mr. Walsh with a lengthy statement. She declared Mr. Trump put out “clear objectives” that would bring the end to Iran’s “brutal attacks and threats.”

Mr. Walsh seemed less than satisfied.

“This operation seemed like a bad idea to me before it happened, and I said so,” he wrote after Ms. Leavitt’s response. “Now that it is happening, I’m not going to suddenly change my tune. It still seems like a bad idea to me. I hope I’m wrong. But that’s how I see it.”

The Iran strikes are far from the first time that the president has tested his base’s capacity to support actions that violate his campaign promise to stay out of foreign conflicts. When he faced questions over whether his supporters would protest after U.S. forces attacked Venezuela, Mr. Trump had a succinct reply.

“MAGA is me,” he told NBC News. “MAGA loves everything I do.”

In recent months, the Make America Great Again movement has started to splinter over key issues, including Mr. Trump’s handling of the Epstein files and his struggles to address rising costs.

Raheem Kassam, the editor in chief of The National Pulse and a conservative activist, said the war with Iran would exacerbate those tensions.

“It’s not something I would have done, but it is definitely something Trump would have done,” he said. “He loves the idea of finishing the job that his predecessors couldn’t even start.”

Mr. Kassam said that Mr. Trump’s supporters trusted him to avoid U.S. casualties more than any of his predecessors, but expressed worries that the conflict does nothing to address a major vulnerability for the president.

He said Americans will only be “just starting to feel better about the economy right as they start voting because they spent too much time on Elon Musk’s failed DOGE project,” arguing Mr. Musk had failed to meaningfully cut government spending. He added: “I agree with the critics that is a big problem.”