As the war in Iran threatens to imperil United States President Donald Trump’s legacy, the political stakes also are rising for two of his top lieutenants: Vice President JD Vance and Secretary of State Marco Rubio. The pair, widely viewed as potential successors to Trump, have been thrust into still-developing negotiations to end the war at a moment when the Republican Party is already weighing its post-Trump future. Vance has taken a cautious approach, reflecting his scepticism toward prolonged US military involvement, while Rubio has aligned himself closely with Trump’s hawkish stance and emerged as one of the administration’s most vocal defenders of the campaign. Trump has said both men were involved in efforts to force Iran to accept US demands to dismantle its nuclear and ballistic missile programmes and allow oil traffic to pass freely through the Strait of Hormuz. With the next presidential election due in 2028 and term limits barring Trump from running again, the president has been putting the succes...