President Obama waves after speaking to service members at the Naval Station Rota, in southwestern Spain on July 10. (Jorge Guerrero/Agency France-Presse/Getty Images)

The dire results of President Obama’s experiment in downsizing U.S. leadership are obvious overseas, but there’s a damaging consequence at home that gets less attention: The mistake builds on itself. It is the opposite of self-correcting.

As the United States withdraws from the world, in other words, the world grows messier and uglier — and that only confirms for many Americans that any involvement is foolish and futile.

This feedback loop fuels the kind of isolationism we’ve seen this year from Donald Trump and Bernie Sanders. It helps explain why there was little talk about foreign policy, beyond chest-thumping about defeating the Islamic State, at the conventions. It will make Hillary Clinton’s job that much harder if she is elected and seeks public and congressional support for a more traditional U.S. leadership role.

The Democratic platform adopted last week boasts that the United States is “stronger abroad and safer at home because of [Obama’s] principled leadership.” As evidence, Obama in his convention speech cited bringing U.S. troops home, killing Osama bin Laden, the nuclear deal with Iran, the opening to Cuba and the global treaty on climate change.

These are genuine accomplishments, even if some are more prospective than proven. But it would be hard for any fair-minded observer to say the world is in better shape today than it was eight years ago.

Iraq, which was unified and mostly peaceful in 2009, is in flames again, and Syria is in even worse shape. The Islamic State has achieved what al-Qaeda never could, controlling territory from which it launches destabilizing attacks in France, Belgium and elsewhere. It is establishing outposts in Afghanistan, Northern Africa and beyond.

Chaos in the Middle East has spun off millions of refugees who have proved so traumatizing to Europe that the continent’s great accomplishment of the past half-century, political union, is in jeopardy. In a stunning violation of post-World War II norms, one European country has invaded and occupied part of another, and no one expects Crimea or eastern Ukraine to be restored anytime soon.

Meanwhile, democracy is in retreat. Repression has intensified inside Russia and China, and both countries are spreading their models of intolerant authoritarianism. Formerly democratic allies such as Turkey and Thailand are moving or have moved into the camp of dictatorships. U.S. engagement has not moderated Iran’s support for terrorism or Cuba’s squelching of dissent. North Korea’s nuclear weapons program is advancing.

Obama is no isolationist, and of course this isn’t all his fault. But his policies of retrenchment contributed: ending the U.S. presence in Iraq, standing aside as Syria dissolved, failing to enforce the red line he had drawn, abandoning Libya after overthrowing its dictator, tamping down U.S. support for democracy and human rights in many parts of the world.

Rather than make the case to the American people that U.S. leadership is in their longtime interest, he reassured them that it was safe to pivot to nation-building at home. As Syria descended into a humanitarian catastrophe unlike any since Rwanda, the president justified inaction by insisting with increasing vehemence on America’s inability to influence overseas events for the better.

Ironically, perhaps, even while bad-mouthing U.S. capacity, Obama toward the end of his presidency reversed course to some extent, much as Jimmy Carter did toward the end of his term after the Soviet Union invaded Afghanistan. Obama sent thousands of U.S. troops back to Iraq and gave up on his plan to pull all troops out of Afghanistan. But he has not accompanied action with rhetoric; he insists the troops in Iraq are not in combat, and he does not lay out a strategic case to explain his reversal to the American people.

Given Trump’s ignorant bombast, his dismissal of allies and admiration for dictators, a focus on Obama may seem beside the point. Obama, like Clinton, and like Mike Pence for that matter, is within the bounds of America’s postwar foreign-policy consensus, which has always accommodated debate about the proper level of U.S. activity overseas and the proper balance between idealism and realism. Trump is well outside the bounds of that consensus.

But even if Trump is defeated, it’s far from clear that Clinton will be able to restore U.S. leadership, both because the world will be in worse shape than it might have been and because the consensus for leadership will have eroded. History may show Obama’s retrenchment to have been one more dip in the traditional Cold War cycle between assertiveness and retreat — or the beginning of a longer turning inward that could end up making the world a far more dangerous place.

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