When President Barack Obama negotiated a nuclear deal with Iran more than a decade ago, his point man was Secretary of State John Kerry. Over 20 months of talks, Mr. Kerry met with his Iranian counterpart on at least 18 different days, often several times per day.

High-level nuclear diplomacy was a natural role for the top U.S. diplomat. Secretaries of state traditionally take the lead on the country’s biggest diplomatic tasks, from arms control treaties to Israeli-Palestinian agreements.

But as President Trump prepares to send a delegation to the latest round of U.S.-Iran talks in Pakistan this weekend, his secretary of state, Marco Rubio, will remain where he often does: at home.

Mr. Rubio did not attend the last U.S. meeting with Iran earlier this month. Nor did he join several meetings held over the past year in Geneva and Doha. Mr. Rubio has also been absent from U.S. delegations abroad working to settle the war in Ukraine and Israel’s war in Gaza. Despite a long period of crisis and war in the region, he has not visited the Middle East since a brief stop in Israel last October.

In recent months, Mr. Rubio — consumed with his second role, as Mr. Trump’s national security adviser — has not traveled much at all.

During the Biden administration, Secretary of State Antony J. Blinken made 11 foreign trips from January 2024 to late April 2024, stopping in roughly three dozen cities, according to the State Department. So far this year, Mr. Rubio has visited six foreign cities, including a stop in Milan for the 2026 Winter Olympics.

Mr. Trump has outsourced much of his diplomacy to others, including his friend Steve Witkoff, a wealthy associate from the world of Manhattan real estate, and his son-in-law, Jared Kushner. Mr. Witkoff and Mr. Kushner have spearheaded diplomacy with Israel, Ukraine and Russia, as well as Iran, whose delegation they will meet for the second time this month in Islamabad, Pakistan’s capital.

Mr. Rubio’s distance from the trenches of diplomacy reflects his dual role on Mr. Trump’s national security team. For the past year, he has served as the White House national security adviser even while leading the State Department — the first person to do so since Henry A. Kissinger in the mid-1970s.

The secretary of state runs the State Department, overseeing U.S. diplomats and embassies worldwide, as well as Washington-based policymakers. Working from the White House, the national security adviser coordinates departments and agencies, including the State Department, to develop policy advice for the president.

The twin roles reflect Mr. Rubio’s influence with Mr. Trump, and offer him a way to maintain it. For Mr. Rubio, less time abroad means more time at the side of an impulsive president prone to making critical national security decisions at any moment.

As Mr. Witkoff, Mr. Kushner and Vice President JD Vance met with Iranian officials in Pakistan earlier this month, Mr. Rubio was at Mr. Trump’s side at an Ultimate Fighting Championship event, noted Emma Ashford, an analyst of U.S. diplomacy at the nonpartisan Stimson Center in Washington. “Rubio clearly prefers to stay close to Trump,” Ms. Ashford said.

Mr. Rubio accepted the national security adviser job on an acting basis last May after Mr. Trump reassigned the job’s previous occupant, Michael Waltz. But officials say that Mr. Rubio is expected to keep it indefinitely.

That arrangement is not inherently bad, Ms. Ashford added. And she noted that previous presidents had entrusted major diplomatic tasks to people other than the secretary of state. President Joseph R. Biden Jr. delegated his C.I.A. director, William J. Burns, to handle diplomacy with Russia and cease-fire negotiations between Israel and Hamas, for instance.

But she echoed the complaints by many current and former diplomats that Mr. Rubio seems less like someone performing both jobs than a national security adviser who sometimes shows up at the State Department. “I do think it’s to the detriment of the whole department of State and to America’s ability to conduct diplomacy in general that we effectively have the secretary of state position sitting vacant,” she said.

Tommy Pigott, a State Department spokesman, contested such claims. “Anyone trying to paint Secretary Rubio’s close coordination with the White House and other agencies as a negative could not be more wrong,” he said. “We now have an N.S.C. and State Department that are totally in sync, a goal that has eluded past administrations for decades.”

Mr. Rubio divides his time between the State Department and the White House, often spending time at both in the same day. In an interview with Politico last June, Mr. Rubio said he visited the State Department “almost every day.”

While there, he often meets with visiting dignitaries before returning to the White House. Last week, Mr. Rubio presided over a meeting at the State Department between Lebanese and Israeli officials that set the stage for a cease-fire in Lebanon.

His twin jobs “really do overlap in many cases,” he said. “In many cases you end up being in the same meetings or in the same places; there’s just one less person in there, if you think about it,” Mr. Rubio added. “A lot of people would come to Washington, for example, for meetings, and they’d want to meet with the national security adviser and then meet with me as secretary of state. Now they can do both in one meeting.”

Asked about his travel schedule during a news conference last December, Mr. Rubio said he had less reason to travel abroad because “we have a lot of leaders constantly coming here” to visit Mr. Trump at the White House. Mr. Rubio also joins Mr. Trump’s foreign trips in his capacity as national security adviser.

Many national security veterans call the arrangement unwise, saying that both jobs are extremely demanding and incompatible with one another.

It was not easy even for Mr. Kissinger, who had firmly established himself over more than four years as national security adviser before convincing President Richard M. Nixon to let him take on an additional role as secretary of state in 1973. (In a reversal of Mr. Rubio’s approach, Mr. Kissinger was in constant motion, including a round of Middle East shuttle diplomacy that kept him on the road for 33 straight days.)

“In general, it’s a mistake to combine those roles,” said Matthew Waxman, who held senior roles at the National Security Council, State Department and the Pentagon during the George W. Bush administration.

“That said, it’s not necessarily a bad thing that a dual-hatted Rubio is so offscreen right now,” Mr. Waxman added. “Especially while so much attention is focused on high-wire diplomacy with Iran, someone needs to manage foreign policy around the rest of the world.”

When Stuart Sepulvida arrives at St. Francis de Sales Roman Catholic Parish in Tucson, Ariz., for Mass, which he attends most mornings, he passes a display honoring local soldiers and encouraging parishioners to pray for their safety. Hundreds of small cards record their names: Robles, Arenas, Grajeda. A portrait of Pope Leo XIV hangs across the lobby.

Mr. Sepulvida, 81, is a Vietnam veteran whose patriotism and Catholicism are deeply intertwined. He voted for President Trump three times but has never felt more betrayed by an American president than when Mr. Trump denounced Pope Leo as “weak on crime” and “terrible for foreign policy.”

“It was very disturbing to me to hear both of them clashing like they did,” Mr. Sepulvida said, standing outside the church one morning this week. Now, he is reconsidering whether he will vote Republican this year.

The Republican Party is struggling to hold onto the support from Hispanic voters who helped propel Mr. Trump back into the White House in 2024. Yet as many party leaders have acknowledged the urgent need to stop the backsliding among Latinos, the president has enraged many of even his strongest supporters by clashing with the pope.

On Easter Sunday, Pope Leo, the first U.S.-born pontiff, spoke of the need to “abandon every desire for conflict, domination and power, and implore the Lord to grant his peace to a world ravaged by wars.” Within days, Mr. Trump, who has led the United States into a war with Iran, said the pope was “catering to the radical left” and posted an AI-generated image portraying himself as a Jesus figure. Mr. Trump later deleted the image, saying he thought it depicted him as a doctor.

“It just isn’t what a president should do,” Mr. Sepulvida said. “The pope speaks for his people. He is beyond politics.”

Mr. Trump won 55 percent of Catholic voters in the 2024 election, compared to 43 percent who voted for former Vice President Kamala Harris, according to Pew Research Center. The most sizable gains came from Hispanic Catholics. While Joseph R. Biden Jr. won their votes by a 35-point margin in 2020, the Democratic advantage shrunk to 17 points in 2024. Now, just 18 percent of Hispanic Catholics said they support most or all of President Trump’s agenda, according to a poll from Pew released earlier this year.

If the president’s quarrel with the pope sours more Latinos on the Republican Party, it could affect midterm races across the country, including in South Florida and South Texas, where Republicans have notched important victories in predominantly Hispanic districts in recent years.

In Arizona’s Sixth Congressional District, which stretches from north of Tucson to the Mexican border, voters were still grappling with the fallout this week.

The district is roughly evenly divided among Republicans, Democrats and independent voters. Nearly a third of the district is Hispanic, and there is a significant population of members of the Church of Jesus Christ of Latter-day Saints, as well as a large Catholic community with deep history in the region. It also has one of largest numbers of military veterans of all congressional districts in the country.

“The president is looking for a lot of attention from everything,” said Maria Ramos, 60, who regularly attends weekday Mass at St. Francis. A registered independent, she usually votes for Democrats but often declines to cast a ballot if she views a candidate as too liberal. “He believes he can put God in his place. He’s meddling in countries that he’s not in control of — he wants to control the world.”

“It is not just a very serious lack of respect — it is a mortal sin,” she said, shaking her head. One word comes to her mind again and again, she said: disgust.

Like so many others in southern Arizona, Ms. Ramos has several relatives who serve in the military — a path they saw to both serve the country and as an entry into the stable middle class. Many of them, she said, voted for Mr. Trump for president.

The Tucson district is now widely seen as one of the most competitive in the country. Republican Juan Ciscomani narrowly won the district in 2022, in part by emphasizing his biography as a Mexican immigrant and a devoted father of six children. He is also an evangelical Christian, a group that has driven much of the growth among Hispanic Republican voters in recent years.

Mr. Ciscomani declined a request for an interview, but when a local radio host asked Mr. Ciscomani what he thought of Mr. Trump’s comments “as a man of faith,” the congressman declined to criticize the president but said, “You can trust that you won’t see any meme like that coming out of my account.”

JoAnna Mendoza, the Democrat challenging Mr. Ciscomani this fall, has made her 20-year career in the U.S. Navy and Marines a key aspect of her story on the campaign trail. While she rarely speaks about her religious background and no longer considers herself a practicing Catholic, she said she briefly considered becoming a nun as a teenager. She criticized Mr. Ciscomani for not condemning the president’s remarks.

“You can’t make faith a central part of your campaign and then allow this to stand,” she said in an interview.

Across Tucson, Latino Catholics, regardless of their past voting preferences, were similarly quick to condemn the president’s remarks.

When Cecilia Taisipic, 71, heard about it, she said, she winced with shame about her vote for him in 2024.

“I thought he would make the country better, but apparently it’s the opposite,” she said as she left Mass at St. Francis earlier this week. She is so fed up with politics, she said, that she is unlikely to vote at all this year. “When it comes to my faith, I don’t like anybody to challenge it. Now I don’t want to hear anything on the news. I just want to pray.”

Matilde Robinson Bours, 63, teaches a weekly Spanish Bible study class at St. Thomas the Apostle Parish, and like nearly all of the women in her class, she immigrated from Mexico decades ago. She has voted for Republicans in nearly every election since she became a citizen. Though she has never liked President Trump, she said, his comments about the pope enraged her more than anything else he has said or done in the past.

“This surpassed everything, every social and political norm — this is personal to all Catholics,” she said. “The arrogance and ego is disgusting. To think that he is God? The pope has every right and responsibility to talk about peace.”

Still, Ms. Robinson Bours said, nothing will stop her from supporting Republicans again this year. She has been delighted that her adult children have stopped supporting Democrats in recent elections.

“Almost everyone I know thinks the way I do,” she said.

Patricia Martinez, 86, who has attended the same Bible study as Ms. Robinson Bours for years, shook her head in disagreement. She said she cannot imagine voting for a Republican who supports Mr. Trump.

“This is different — this shows he is out of his mind,” said Ms. Martinez. “We have to have basic respect and teach that to people in this country.”

Patrick Robles, a 24-year-old native of Tucson, spent years alienated from the Roman Catholic Church, but returned to his faith more recently. “The craziness of the world sort of caused me to seek some sort of answers,” he said. Now, he attends Mass at the St. Augustine Cathedral in downtown Tucson, a few blocks from the office where he works as an aide to Representative Adelita Grijalva, a Democrat.

Mr. Robles said he saw Mr. Trump’s battle with the pope as both a personal affront and a political opportunity.

“The president is basically trying to draw a line between Catholics and what we perceive to be patriotism,” he said. “I believe we can be both.”

Last week, he texted one of his uncles who has supported Mr. Trump in every election asking him what he thought.

“I’m afraid we need divine intervention,” the uncle replied.