As the ongoing Iran war threatens to shape the legacy of Donald Trump, it is also intensifying the political rivalry between two of his top allies — Vice President JD Vance and Secretary of State Marco Rubio — both seen as leading contenders for the 2028 presidential race.

With Trump barred from seeking another term, the question of succession is gaining urgency within Republican circles. According to sources familiar with his thinking, Trump has privately asked advisers a simple but significant question: “JD or Marco?”

Both Vance and Rubio have been deeply involved in efforts to end the Iran conflict, now in its fifth week, but their approaches differ sharply. Vance has taken a more cautious stance, reflecting skepticism toward prolonged U.S. military involvement abroad. In contrast, Rubio has aligned closely with Trump’s more hawkish position, emerging as one of the administration’s strongest advocates for the campaign.

Trump has said both men are playing key roles in pushing Iran to accept U.S. demands, including dismantling its nuclear and ballistic missile programs and ensuring the free flow of oil through the Strait of Hormuz.

Political analysts say the outcome of the war could significantly influence their 2028 prospects. A swift and favorable resolution for the United States could strengthen Rubio’s credentials as a steady crisis manager. However, a prolonged conflict might benefit Vance, allowing him to appeal to anti-war sentiments within Trump’s political base.

The president’s own standing appears to be under pressure. A recent Reuters/Ipsos poll showed Trump’s approval rating dropping to 36%, its lowest since returning to office, amid rising fuel prices and public dissatisfaction with the Iran war.

Within Republican ranks, there is growing speculation over Trump’s preference. Some insiders believe he may be leaning toward Rubio, citing his visible role in defending the administration’s policies. However, the White House has dismissed such claims, insisting there is no favoritism.

Vance, 41, a former Marine and Iraq War veteran, has long argued against U.S. entanglement in foreign conflicts. Despite past differences, he has publicly supported Trump’s handling of the Iran crisis. Meanwhile, Rubio, 54, has set aside past political rivalries with Trump and now maintains a strong working relationship with the president’s team.

Recent polling among conservative activists reflects the competitive nature of the race ahead. At the Conservative Political Action Conference, Vance led a straw poll with 53% support, while Rubio gained ground with 35%, a sharp rise from the previous year.

Observers say the Iran conflict could prove decisive. A successful outcome may politically reward those seen as decisive leaders, while a drawn-out war could complicate the ambitions of both men.

For now, Trump appears to be keeping his options open, with one senior official noting that he is reluctant to “anoint” a clear successor — leaving the “JD or Marco” question unresolved as the 2028 race slowly takes shape.