Who would lead if Khamenei falls? Rubio briefs Senate on Iran situation

US Secretary of State Marco Rubio warned American lawmakers that the future of Iran’s leadership remains hugely uncertain — a complexity he says far exceeds even the dramatic events unfolding in Venezuela.

Rubio’s comments signal a cautious shift in Washington’s strategic thinking as tensions with Tehran escalate and the decades-old Iranian political system faces mounting internal pressures.

US President Donald Trump threatened possible military action against the regime, warning that an “armada” is heading toward Iran even as US forces are staging major multi-day drills in the Middle East.

'No one knows'

Speaking Wednesday at a Senate Foreign Relations Committee hearing primarily about recent US operations in Venezuela, Rubio was asked how the United States would handle a potential power vacuum in Iran should Supreme Leader Ayatollah Ali Khamenei — in power since 1989 — be removed or otherwise depart.

Rubio's response: “No one knows”.

In saying this, Rubio underscores the entrenched and opaque nature of Iran’s political structure, as per US media reports.

The difficulty, Rubio explained, stems from the way Iran’s system is built: ultimate authority is concentrated in the office of the supreme leader, supported by institutions such as the Islamic Revolutionary Guard Corps (IRGC) and religious oversight bodies that intertwine clerical authority with state power.

Outcome unpredictable

Because these structures have evolved over decades, any disruption at the top could lead to unpredictable outcomes — far more so than the relatively clearer transition dynamics seen in Venezuela after the ousting of Nicolas Maduro.

Rubio’s remarks came amid increasing turmoil inside Iran, where economic hardship and nationwide protests have persisted since late 2025.

Rubio characterised the regime as “probably weaker than it has ever been,” though still resilient and capable of suppressing dissent.

For US policymakers, the implications are significant: without a clear succession path, any plan for regime change or power transition would require intensive analysis, diplomatic engagement, and contingency planning.

Careful thinking

Rubio emphasised that careful thinking would be essential if Washington ever seriously contemplated such an eventuality.

At the same hearing, Rubio also defended the continued presence of tens of thousands of US troops in the Middle East, framing it as a defensive posture against potential threats from Tehran’s arsenal of drones and missiles.

That stance comes alongside broader US pressure on Iran over its nuclear programme and warnings from President Trump that “time is running out” for a diplomatic deal to avert military confrontation.

Analysts say Rubio’s acknowledgment of uncertainty over Iran’s future leadership reflects deeper challenges for US strategy.

Unlike Venezuela — where a clear interim government now claims authority — Iran’s theocratic system lacks straightforward mechanisms for succession, and the Assembly of Experts, the body constitutionally tasked with choosing a new supreme leader, has not publicly signalled a successor to Khamenei.

As Tehran’s domestic situation evolves and Washington continues to grapple with its approach — balancing deterrence, diplomatic pressure, and contingency planning — the question of “what comes next” will remain at the heart of US foreign policy debates.