In the 1997 movie “Wag the Dog,” a political adviser manufactures a war to help a scandal-besieged president win reelection. This parallel came to many minds after President Trump ordered airstrikes that killed Iran’s Quds Force commander, Maj. Gen. Qasem Soleimani.

After all, Trump himself repeatedly predicted that President Barack Obama would start a war with Iran to help his reelection efforts, suggesting that perhaps Trump thinks that starting a war in an election year is a plausible strategy for winning voters. But political science research suggests otherwise.

Voters are most likely to rally around the flag when there is bipartisan elite support

The “rally around the flag” effect happens when international crises increase support for the president at home. This effect is a major reason some might suspect that attacking Iran would be politically beneficial for the president.

For example, the approval ratings of presidents George H.W. Bush and George W. Bush immediately surged after their respective military interventions against Iraq. Trump seemed to literally want Americans to rally around the flag when he tweeted a picture of the American flag soon after Soleimani’s demise.

But not all military crises trigger rally effects. Political science research shows that rally effects are most likely to occur when there is bipartisan support among political elites for the president’s actions.

This was true even for the enormous outpouring of support for George W. Bush after the 9/11 terrorist attacks. Cindy Kam and Jennifer Ramos showed that the patriotic rally behind Bush eroded after Democrats ended their moratorium on criticizing the Republican president.

Of course, Democratic elites have not provided any grace period before starting to criticize President Trump. Democratic leaders quickly condemned the president for ordering the airstrike against Soleimani without informing them, saying that the administration lacked any broader strategy for dealing with Iran.

The absence of bipartisan support for a deeply polarizing president’s actions makes it highly unlikely that attacking Iran will rally Americans in support of Trump.

War has not helped incumbents win reelection

Nor would a larger war against Iran increase Trump’s odds of reelection. In fact, research suggests it would have the opposite effect.

Douglas A. Hibbs’s famed Bread and Peace model argues that two factors explain most of the variation in presidential election outcomes since 1948: The positive effects of real disposable income growth and the negative effects of cumulative U.S. military casualties from unprovoked, hostile deployments of American armed forces in foreign wars.

This research suggests that the Democratic Party paid an electoral price for committing U.S. forces in Korea and Vietnam. The Iraq War also appeared to undermine support for George W. Bush’s reelection. Despite narrowly winning in 2004, Bush won fewer votes than expected for an incumbent president in a growing economy.

An armed conflict with Iran that results in American casualties would therefore probably hurt Trump in 2020 rather than help him.

Military action against Iran is unpopular

That is especially true considering the state of public opinion. Unlike the strong initial support for military deployments in Korea, Vietnam and Iraq, the American public has shown little appetite for war against Iran.

A July Gallup Poll found that 78 percent of Americans preferred diplomatic efforts over military action to prevent Iran from acquiring nuclear weapons. Nearly two-thirds of respondents in that survey were worried that the United States will be too quick to use military force against Iran.

A September poll commissioned by the University of Maryland showed similar results. Only 20 percent of Americans in that survey said that the United States should be prepared to go to war with Iran to achieve its goals, compared to 76 percent who said that U.S. policy goals do not warrant waging war.

To be sure, military action against Iran will probably grow more popular as Trump’s supporters rally to defend the president’s actions. Americans often change their opinions about foreign policy based on their views of the president who is guiding it.

But that will not change the fundamental lessons from prior academic research: Attacking Iran will not help Trump win reelection.

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