WASHINGTON — President Donald Trump’s boycott of this weekend’s Group of 20 summit in South Africa leaves the forum fumbling to divine his latest intentions on the global stage without a U.S. representative for the first time since its inception.

Fortunately, world leaders can find insight in the foreign policy machinations of the U.S. president’s top two lieutenants: Vice President JD Vance and Secretary of State Marco Rubio. Although those around them insist that there’s no mutual rivalry, it hasn’t curbed their boss’ impulse to fuel an "Apprentice"-style contest on the global stage.

Both the Republican stars, who have each chased White House dreams, have closely aided Trump as he sketches out the bones of a new foreign policy. Paying attention to their divergent styles and interaction offers clues to reading the emerging doctrine espoused by the U.S. administration — as well as a gauge of who might take on the mantle for the 2028 race.

Rubio, 54, a longtime anti-Communist hawk, has embraced Trump’s aggressive approach while seeking ways to deal in private. Vance, 41, a relative newcomer to politics best known for a memoir about life in small-town Ohio and Kentucky, embodies the Make America Great Again movement’s anti-elite sensibilities, plus Trump’s penchant for disruptive and unpredictable dealmaking.

“This is a mythical fairytale Romulus and Remus, the sons of MAGA,” said Matthew Bartlett, a State Department appointee during Trump’s first term. “Vance, a biblical conversion, from a private critic to MAGA spokesman. Rubio, who ran against Trump, this establishment figure who now continues to be one of the most articulate spokesmen of his foreign policy.” While the foundational legend of ancient Rome resulted in bloodshed, the pair have downplayed any sense of competition. Vance has named Rubio “my best friend in the administration.” Rubio in July called Vance a "close friend" and said he "would be a great nominee."

A person close to the Secretary of State who requested anonymity to describe internal dynamics said there's a spirit of collaboration and trust between them built through a relationship of recent years. The pair developed a bond on Capitol Hill, as Vance found himself a youthful, Catholic senator with young children navigating Washington after his election in 2022.

The experience was similar to the one Rubio lived through a decade before, the person said. Trump, though, keenly aware of his own ticking clock at the White House, has spent months privately — and at times publicly — teasing of a rivalry between the two, suggesting at turns that one, then the other, is best positioned to take the torch from him. People close to Trump say much of that banter is designed to stave off any sense of the president as a lame duck.

On Air Force One recently, Trump aired those musings publicly, saying: “We have JD obviously, the vice president, who’s great. Marco’s great. I’m not sure if anyone would run against those two. I think if they ever formed a group it would be unstoppable.”

Many in Trump’s orbit see Vance as the heir apparent and also privately downplayed any talk of a rivalry. Rubio, who ran for the Republican nomination in 2016, often clashing with Trump as they vied for the same prize, has been careful not to encourage any 2028 talk. State Department spokesman Tommy Pigott said that Vance and Rubio "have an incredible relationship, both personally and professionally."

Yet Rubio, a Florida native, was also on Trump’s running-mate shortlist before Vance was selected. And the vice president himself acknowledged that Rubio could eventually mount another presidential campaign, telling Fox News the pair would “cross that bridge when we come to it.”

The recent Gaza ceasefire deal showcased the different roles of the two men. As the U.S. closed in on the accord, it was Rubio who quietly slipped the president an urgent note during a public meeting, telling him it was ready. Some weeks later, as the fragile arrangement teetered, Vance was the one dispatched to Israel to keep it on track. Rubio arrived to reinforce it just hours after Vance’s plane left the country.

Alex Wong, who served as principal deputy national security adviser during the first part of the year, recalled another instance where Rubio and Vance worked together as a tag-team to ease a tense moment between India and Pakistan after a terrorist attack unfolded as Vance was on a visit to the region. As Rubio engaged with his counterparts to try to bring down tensions, Vance pursued direct conversations with Prime Minister Narendra Modi, with whom he had worked to build a relationship, Wong said.

“That was a pretty high tension and delicate diplomatic endeavor over a period of two weeks,” he said. “And it resulted in the missiles stopping and an agreement to stop the fighting on both sides.”

India, it should be said, disputes that the U.S. brokered any such deal with Pakistan.

In the early days of Trump’s second term, both Vance and Rubio played a part in shoring up the president’s attempts to assert a U.S. sphere of influence throughout the Americas. It was Vance who became the highest-ranking U.S. official to travel to Greenland when he took a trip with his wife, Second Lady Usha Vance, criticizing Denmark’s treatment of its territory while there.

For his part, Rubio became the first Secretary of State in more than a century to make his first solo trip to Central America, beginning in Panama, where control of the canal is another object of Trump’s desire.

In more recent days, Rubio met with counterparts at a G-7 foreign ministers gathering in Canada, demonstrating that some traditional closed-door diplomacy continues. Vance’s planned appearance at the G-20 summit in Johannesburg in place of Trump was canceled amid the president’s clash with South Africa’s leaders. Some in South Africa privately expressed relief at his absence.

From a global perspective, many foreign allies have preferred dealing with Rubio, finding his more reserved style, experience, practicality, and background as a more traditional Republican hawk easier to work with than Vance’s abrasive hectoring.

Some counterparts have known Rubio for years from his time on the Senate Foreign Relations Committee. But capitals have taken notice of the platform Vance has, as he has traveled the world on behalf of the president.

“Secretary Rubio has to deal day-to-day with solving these problems in a tactical level,” said Alexander Gray, who served as chief of staff on the National Security Council during Trump’s first term. Vance, he said, “is providing the intellectual ballast about what a future Republican foreign policy is going to look like.”

The vice president stepped into a visible public role on foreign affairs and has been closely engaged privately as well, though insiders stress that Trump is driving the policy. Nowhere is that clearer than on China, where Trump is relying on his business instincts and personal relationship with President Xi Jinping to keep trade relations on track. Vance, however, ran point on a deal to take control of social-video platform TikTok’s U.S. operations.

That fits with his role as attack dog — even troll — to allies and adversaries alike. Vance is very online and has adopted a confrontational style on social media, occasionally using coarse language, and shows little hesitation in picking fights.

Vance’s signature breakout moment came in February at the Munich Security Conference, where he delivered a fiery speech arguing Europe’s greatest threats were “internal” and not top adversaries Russia or China, sending shockwaves through the continent. “There’s a new sheriff in town,” he declared at the time.

That same month, he had an explosive Oval Office exchange with Ukrainian President Volodymyr Zelenskyy, criticizing him for what he described as insufficient gratitude toward Trump. Not long after, the Trump administration temporarily suspended military aid and intelligence sharing with Kyiv.

While European officials speak highly of Rubio and say his grasp of foreign policy issues is impressive, views are more mixed on Vance.

People close to the White House note Vance has been deeply involved in key foreign policy discussions and has gotten involved on the granular level, but they question how much influence he has when it comes to crafting or driving policy. Some said that they see him more focused on reading the MAGA base and making sure that the administration reflects their priorities than engaging with foreign leaders.

White House communications director Steven Cheung said Trump “frequently turns” to Vance, as well as members of his Cabinet, “for important input and insight into a variety of foreign policy issues." Cheung described Vance as a "trusted, loyal, and influential advisor to President Trump and his entire team."

Special Envoy for Peace Missions Steve Witkoff described a collaborative dynamic between himself and Vance and Rubio, and argued Vance had been “completely integral” in foreign policy discussions.

“I’ve never seen him chair a meeting in the Situation Room and need to be in the lead chair just to be there, just to sort of rubber stamp who he is because the President might not be there,” Witkoff said. “He doesn’t operate like that. He’s there because he thinks he can be impactful.”

Vance faces the classic dilemma of every vice president: Regardless of his personal position on an issue, he's a key spokesperson for the administration who needs to be in lockstep with the president. The leaked Signal chat that was published by The Atlantic earlier this year provided a rare behind-the-scenes look at the Vice President appearing to break with Trump over airstrikes on the Houthis in Yemen.

In the chat, Vance said, “I think we are making a mistake,” and added, “I am not sure the president is aware how inconsistent this is with his message on Europe right now." When asked later by Fox News about how the strikes eventually were carried out, Vance said, "I think the president had made his desires clear and our job is to implement it."

In May, Rubio took on the additional role of interim White House national security adviser. While Trump at the time predicted he would name a new permanent adviser within six months, that deadline came and went. Both Trump and Rubio are happy with the current arrangement, which made Rubio the only person besides Henry Kissinger a half century ago to hold both jobs. People familiar with Trump’s thinking say he isn’t currently contemplating anyone else for the role.

The Trump administration’s Latin America policy bears the hallmarks of Rubio’s hawkish record on Venezuela’s authoritarian leader, Nicolas Maduro, since Trump’s first term.

Rubio in the executive branch has still needed to sublimate some of the idealism that he expressed publicly as one of 100 senators. A decade ago, he called Russian leader Vladimir Putin a “gangster” and “thug” and hammered Trump’s then-nominee for secretary of state in early 2017 for refusing to call Putin a war criminal. He has needed to be more pragmatic as America’s top diplomat, joining Trump and Witkoff for a three-on-three meeting with Putin and Russian officials in Alaska in August.

Yet Rubio also has shown the limits of his accommodation. In October, after Trump floated the idea of another meeting with Putin, Rubio spoke with Russian Foreign Minister Sergei Lavrov and quickly assessed that Moscow hadn’t made any substantive changes to its position on Ukraine that would justify another summit, U.S. and European officials told Bloomberg News at the time. Trump called off his plans.

Rubio last week said that Trump will only agree if there is a significant opportunity to help end the war in Ukraine. One person familiar observed that Rubio patiently waited for Witkoff’s engagement approach with Russia to run its course and then was able to step in and inject more skepticism.

The dynamic may inevitably lead to a clash down the road. For now, however, the vice president is tamping down talk of any rivalry.

“If either of us end up running, it’s a long ways in the future and neither of us is entitled to it,” Vance told Fox News last week. “So I think it would be ridiculous for me to say Marco is a rival. No, Marco is a colleague.”

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With assistance from Alberto Nardelli.

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