US-Iran Conflict: Emboldened Trump Seeks Legacy in Iran, But Domestic Constraints Lie Ahead

The large-scale United States (U.S.)-Israeli military campaign against Iran embodies U.S. President Donald Trump’s second-term foreign policy approach of being more interventionist overseas and embracing strategic military operations. Trump seeks to establish a foreign policy legacy that demonstrates US strength and corrects the perceived ‘failures’ of his predecessors.
The U.S. actions in pursuit of these ambitious objectives, and Iran’s retaliation, have moved the conflict immediately to a scenario of a short-lived but large-scale campaign with significant implications for the Middle East and the global economy. Trump has committed to a campaign of up to 4-5 weeks and acknowledged that the lives of some American military personnel will be lost.
This is a clear shift from his first-term foreign policy rhetoric, where he criticised previous U.S. interventions that lost lives, which BMI analysts believe highlights his more emboldened foreign policy approach this term and his recognition of the opportunity for his legacy from military action against Iran now.
Domestic opinion could alter Trump’s calculus. Trump’s approval rating on foreign policy before the strikes on Iran was low, with only 40% of Americans approving of his approach. His approval ratings fell sharply in January after U.S. military action in Venezuela and his threat to take over Greenland. Despite an uptick in approval after the weekend's actions in Iran, the low approval generally signals Americans’ aversion to overseas military action. BMI expects Americans to be even more cautious of action in the Middle East, with protracted conflicts in Afghanistan and Iraq, as well as elevated energy prices, still fresh in their minds.
Trump will also be sensitive to any negative economic impact from the conflict, especially the potential of higher U.S. inflation due to an oil price shock, as well as a sharp rise in bond yields. He is already under pressure on affordability (only 36% of Americans approve of his approach to inflation). Although BMI does not expect Trump to change course if the campaign proves short-lived, given little long-term price disruption, anything more protracted may do so.
Of note, a prolonged campaign that causes a significant oil price spike to US$110-130 per barrel (/bbl) (from the baseline forecast of US$67/bbl for 2026) over the next quarter could increase average U.S. inflation by up to 1.1 percentage point (pp) from the 2026 forecast of 2.3%, which would be enough for Trump to change course and seek a quick end to the conflict.
Finally, Congress is not expected to force Trump to end the conflict, despite it considering a war powers resolution this week. This is primarily due to the fact that enough members of Congress appear to support the administration’s military actions against Iran. If it did pass, the administration would still have a minimum of 60 days to end its actions without further Congressional approval. BMI does not expect that Trump would want to continue military action beyond that length of time, meaning such a vote would not change his strategy.

(Source: BMI, A Fitch Solutions Company)