President Donald Trump begins his conflict with Iran on a narrow ledge in public opinion. So long as the mission’s costs to America remain small, he’s unlikely to face insurmountable political pressure to end it. But he starts the war extraordinarily vulnerable to backlash if things go wrong.

Polls show that most Americans do consider the Iranian nuclear program a threat. But in one January survey, 70% of all Americans (and 80% of independents) said they opposed military action in Iran. Similar proportions of both groups said any president should obtain approval from Congress before initiating military action.

Yet Trump took the nation to war with Iran after only the most cursory effort to build public support. That’s unlikely to be reassuring to the solid majority of Americans — around 55% according to an AP/NORC survey released last week — who express little or no confidence in Trump’s ability to make decisions about the use of force abroad, or to manage relationships with either international allies or adversaries.

Trump’s choice to assail Iran solely with airstrikes hints that at some level he recognizes that he faces greater political limits than he publicly acknowledges. Trump famously told the New York Times in January that he considers his “own morality” and “own mind” the sole check on his ability to deploy force. But Trump’s reluctance to pursue the ground invasion that would likely be necessary to achieve his expansive goals suggests that he’s also constrained by another dynamic: the potential of a public outcry if there are significant U.S. casualties.

Republican voters will surely rally behind the attacks, and few Americans of any political persuasion will mourn the death of Ayatollah Ali Khamenei, Iran’s ruthless supreme leader for nearly the past 40 years. But Trump could quickly face substantial public recoil from not only Democrats but also independent voters if the war results in American deaths, terror attacks here or abroad, or even a spike in oil prices.

If a few days of bombing somehow topple the Iranian regime, Trump almost certainly will receive some political boost. But even that might not last, just as his earlier bombing campaign against Iran and the capture of Venezuelan President Nicholas Maduro produced no durable improvement in his approval rating.

It’s even more difficult to envision Trump politically benefiting from the sort of equivocal outcome that may be most likely — a bombing campaign of moderate duration that damages, but does not dislodge, the regime.

In fact, that outcome could weaken him. One of Trump’s greatest second-term problems is that many voters who supported him in 2024 because of frustration over inflation believe he has focused on almost everything except what they elected him to do. In a CNN/SRSS poll last month, over two-thirds of all adults — and more than three-fourths of independents, young adults and people of color — said Trump had not paid enough attention to the nation’s most important problems. Trump is more likely to reinforce than allay those concerns by launching a war of choice.

Evan Roth Smith, a centrist Democratic pollster, says that just as Republicans in 2024 successfully made the case that Democrats took “their eyes off the ball because of cultural issues, right now there is a case to be made that Donald Trump is too focused on this situation in the Middle East” and other foreign conflicts, rather than the daily financial concerns of average Americans. The downside risk to Trump, Smith says, is probably much greater than the potential upside benefit.

It’s difficult to think of a president who launched an international conflict of this potential magnitude with so little attempt to publicly justify his actions. Even in the lead-up to the 2003 invasion of Iraq, the unilateralist President George W. Bush pursued a much more sustained effort at domestic and international persuasion.

Trump has barely explained why he considers this war necessary; has not indicated how he will define success; and has been indifferent to engaging with Congress. Despite the Castro-esque length of his State of the Union address last week, Trump made only a passing reference to the conflict. He’s offered no serious explanation for how he has evolved from declaring in his first presidential campaign that “Our current strategy of nation building and regime change is a proven, absolute failure” to explicitly embracing regime change as his goal in Iran.

One former senior national security official in a Republican administration told me that “every previous administration in both parties recognized they had to” engage the public, the media and Congress before starting hostilities. “When you go to war you can’t just go to war with your base, you have to go to war with the whole country.” Trump has conspicuously chosen not to follow that model, displaying as little interest in consulting Congress as in enlisting international allies. Instead, Trump has behaved as if he believes he is no longer required to undertake such formalities as gathering consent from the governed.

Yet while Trump is straining the American democratic system in unmatched ways, he and his party still must face voters in November. And his choice to go to war so unmistakably at his own whim means that he unambiguously owns the political consequences. That reality may encourage him to declare victory quickly whatever the conditions on the ground, while he can bask in the success of the initial military strikes and before painful costs start to accumulate.

As the former Republican national security official pointed out to me Saturday, the administration’s immigration enforcement offensive in Minneapolis may offer a window into the president’s calculus. Trump asserted a virtually unbounded vision of presidential authority and trampled traditional approaches to federalism when he dispatched thousands of federal agents into Minneapolis over the opposition of state and local officials. Yet the official pointed out that Trump retreated quickly once a different kind of American casualty — the killings by federal agents of two middle-class, white U.S. citizens — triggered an intense public outcry.

American politics is now a form of trench warfare between red and blue coalitions that are utterly antithetical in their vision for the country, yet almost exactly equal in size. The balance of power between them is held by a thin sliver of swing voters who are motivated far more by their immediate financial concerns than by any other issue, especially foreign policy.

Short of the most severe outcomes — rapid regime change or a quagmire with mounting costs — Trump’s latest military incursion isn’t likely to materially change that fragile electoral balance. What’s more likely is that it further destabilizes the already wobbling balance between an American constitutional system grounded in checks and balances and a president determined to shatter those restraints.

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This column reflects the personal views of the author and does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Ronald Brownstein is a Bloomberg Opinion columnist covering politics and policy. He is a CNN analyst and the author or editor of seven books.

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