The political consequences of the Iran war

If Robert Kagan and other early opponents of the war in Iran are right, the conflict will end in defeat for the United States, an outcome that will irreversibly weaken America’s global standing and will “set off a chain reaction around the world as friends and foes alike adjust to America’s failure.” Even when a war begins with popular support, as many do, failing to achieve its key objectives can affect public sentiment in ways that constrain the ability of leaders to undertake future military action. And when wars are undertaken without initial public support, as the latest conflict with Iran was, the public reaction against those who started and supported it can be harsh.

It is too early to predict the outcome of the war with certainty, but the United States is farther away from achieving its objectives than the Trump administration has been willing to admit. Although the president and senior officials insist that Iran’s military has been destroyed, classified intelligence assessments have concluded that Iran can still field about 75% of its mobile launchers and retains about 70% of its prewar missile stockpile. The evidence suggests that Iran has rebuilt access to 30 of its 33 missile sites along the Strait of Hormuz, which would make it dangerous for the U.S. Navy to escort cargo vessels through the strait. If the assessment is correct, the Iranians have been able to reopen most of their underground storage facilities and repair at least some damaged missiles.

Another report produced for the chairman of the Joint Chiefs of Staff by the Joint Chiefs’ intelligence directorate found that the war with Iran is working to China’s advantage across military, economic, and diplomatic domains. President Xi Jinping’s confident conduct during President Donald Trump’s recent visit to Beijing is consistent with the Pentagon’s assessment.

Kagan’s analysis focuses on the international consequences of failure in Iran, but its effects are likely to ripple through America’s internal affairs as well. Military setbacks tend to reduce public confidence, not only in the administrations that preside over them, but in government as a whole. The public mood darkens, and its confidence in the future declines.

Wars that end in defeat—Vietnam and Afghanistan, for example—diminish public support for military action abroad, as do wars, such as America’s long engagement in Iraq, whose costs are seen as exceeding its benefits, even if the outcome is more ambiguous. When Trump began his presidential campaign in 2015 by denouncing the wars in the Middle East as stupid, many observers thought that Republican primary voters would turn against him. But he had read the mood of the voters more accurately than commentators trapped in the Reagan-era assumption that Republicans were uniformly hawkish. Failed wars have consequences that endure longer than the presidents who start them.

Domestic political effects

The current state of U.S. public opinion

Most wars in modern American history have begun with broad public support, which fades if a war continues over an extended period without yielding clear advantages or a successful outcome. By contrast, the war with Iran was unpopular even before it began, and it has become steadily more unpopular over time. Polls conducted soon after the war began found that by an average of 48% to 43%, a plurality of Americans opposed the war. Polls conducted in May showed disapproval rising sharply to an average of 58%, compared to just 38% who supported the war.

The reasons for the public’s initial negative reaction are clear. Among them: only 25% bought the Trump administration’s claim that Iran represented an imminent threat to the United States, and 56% believed that the administration should have sought congressional approval before initiating hostilities.

By April, the public’s reservations about the war had broadened. More than six in 10 Americans—including nearly all Democrats and 72% of independents—had concluded that Trump did not have a clear plan for the conflict, and two-thirds said that the administration had failed to explain the war’s goals. Asked about specific goals, overwhelming majorities said that the United States had failed to reopen the Strait of Hormuz, permanently stop Iran’s nuclear programs, or ensure freedom for the people of Iran.

A Chicago Council on Global Affairs survey conducted in early May provided the broadest portrait of public sentiment so far. By then, Americans had concluded that the impact of the war was negative for the U.S. cost of living (86%), international relations (72%), overseas reputation (72%), and national security (65%). Majorities of Americans thought that the Trump administration had not done enough to consult with allies and partners in the region, limit U.S. and Iranian civilian casualties, or pursue a negotiated resolution to the conflict. A plurality concluded that the war was stalemated, with neither side gaining a clear advantage. Few Americans expressed confidence that Iran would comply with a deal to end the conflict. Surprisingly, 48%—including 55% of Independents—lacked confidence that the United States would comply either.

It is not hard to see why public sentiments about the war have become more negative since it began. As the interruption of shipping moving through the Strait of Hormuz has raised oil prices above $100 per barrel, Americans are paying much more for gasoline—and for the diesel fuel on which the U.S. trucking industry mostly depends. Because trucks transport more than 70% of goods in the United States, higher fuel costs tend to raise prices throughout the economy. Similarly, the shutdown of shipping raised the prices farmers pay for fertilizer as they entered the spring planting season. The most recent Producer Price Index report, which tracks prices businesses pay for their inputs, showed costs surging by 6% from a year ago, 1.4% in April alone. Consumers are faring no better. The most recent Consumer Price Index showed consumer costs rising by 3.8% from a year ago, the most rapid increase in three years, and enough to wipe out the inflation-adjusted wage gains that workers had made during the past 12 months.

The news is bad on the fiscal front as well. The publicly announced cost of the war continues to rise (the most recent estimate was $29 billion), but the actual costs will be much higher. U.S. weapons stockpiles will have to be replenished, damages to U.S. facilities in the Middle East (which are more extensive than the administration has acknowledged) will have to be repaired, and maintenance costs for ships deployed far beyond their normal rotations are bound to rise.

Weeks ago, the administration surfaced, and then quietly pulled back, a $200 billion supplementary bill for the military. But recent reports of cash shortages to fund ongoing operations suggest that the Pentagon will be forced to make a formal request for supplemental funding well before the end of the fiscal year. The size of the bill is likely to induce heartburn for Congress and the electorate alike. Since the beginning of Trump’s second term, the share of Americans who regard the budget deficit as a very big problem has risen from 57% to 64%, and sharp increases in military expenditures can only intensify this concern.

The longer-term political impact of the Iran war

President Donald Trump. Public approval of Trump’s performance has declined throughout most of his second term, but the Iran war appears to have accelerated the drop. One in four Americans who voted for him in 2024 opposes the war. Since it began, the president’s job approval has declined by more than three percentage points, to just 40%, while his disapproval has risen to 57%.

This matters because a president’s level of public support significantly influences the outcome of the midterm elections. As of the end of May, Democrats’ edge over the Republicans has risen to 6.8 points, a swing of more than nine points from 2024, enough to overcome Republican gains in the national redistricting war, and Democratic prospects in the Senate have brightened as well. A Democratic victory in the House of Representatives would bring the president’s legislative agenda to a halt and expose his administration to the congressional oversight that it has not experienced thus far. A broader Democratic victory extending to the Senate would force the president to account for the opposition’s views on potential nominees, and Make America Great Again (MAGA) stalwarts would be difficult to confirm.

The Republican Party.  The coalition that returned Trump to the White House in November 2024 had three main components: Republicans who identified as supporters of the MAGA movement, Republicans who did not support MAGA, and non-Republicans who saw Trump as preferable to the alternative. Many members of the third group—independents, Hispanics, and young adults—had jumped ship before the war in Iran started. The war has exposed differences between MAGA and non-MAGA Republicans, who are less supportive of the decision to attack Iran, and it has created a rift within the MAGA movement. Led by Tucker Carlson, some MAGA supporters regarded going to war against Iran as antithetical to MAGA’s core beliefs. Some critics of the war charged that Israeli Prime Minister Benjamin Netanyahu had persuaded Trump to start a war that served Israel’s interests more than America’s, adding fuel to eruptions of antisemitic sentiments on the right.

Vice President JD Vance, whose support for MAGA is more ideological than Trump’s, made no secret of his opposition to starting the Iran war. But once the president decided to move forward, the vice president had no choice but to support him. If he decides to seek the Republican presidential nomination in 2028, his balancing act could rekindle charges that he is a man without fixed principles and invite challenges from candidates who insist that “America First” means opposition to wars of choice, especially in the Middle East.

The Democratic Party. At first glance, the war in Iran has worked to the Democrats’ advantage. They are nearly unanimous in opposing it, putting them on the side of a wide majority of the electorate. They have drawn blood by linking the war to high prices and calling attention to the administration’s shifting rationale for the conflict.

On the other hand, some Democrats have embraced the charge that Israel persuaded Trump to initiate a war that serves Israel’s interests more than those of the United States, adding to the anti-Israel sentiment that is rising among the party’s rank-and-file supporters in response to events in the region, especially the war in Gaza, that precede the conflict with Iran. This shift away from the party’s historic support for Israel could induce candidates for the 2028 Democratic presidential nomination to adopt positions that the majority of the electorate finds extreme. Pro-Israel candidates who refuse to trim their sails could be screened out, even if they would be strong nominees for the general election.

Conclusion: Deciding to go to war

As the war passed the 60-day mark, Democrats began a series of attempts to invoke the War Powers Resolution, which would have required the administration to obtain majority support in both the House and the Senate in order to continue the conflict. Although the maneuver failed, more Republicans are now joining in. The most recent effort succeeded in the House by a vote of 215-208 as four Republicans joined with the Democrats to support it.

This strategy rests on a firm foundation of public support. A survey conducted just weeks before the war began found 70% of the electorate agreeing that presidents should receive congressional approval before taking military action against another country.

Even if invoking the War Powers Resolution ultimately receives majority support in both chambers, the administration is unlikely to comply. (The congressional resolution is subject to a presidential veto, and there are no immediate prospects of mustering the two-thirds majority needed to override it.) Still, the fight is likely to increase public awareness of this legal mechanism and reinforce the constitutional principle that the president is not free to take the country to war without congressional assent.

Over the past half century, as executive power has increased at Congress’ expense, presidents of both political parties have violated this principle. In history’s hindsight, it is possible that Trump’s decision to bypass Congress and the American people in Iran will mark the moment at which Congress began to exercise its constitutional prerogatives and unchecked presidential power began to recede. In the short term, invoking the War Powers Resolution is one of the few options opponents of the war can pursue to reflect the public’s desire to end it.