Conventional wisdom says that if you want to be an influential president, you should be a success. But in some ways, the influence of failures is greater. Because of that, one of the areas ripe for debate in the 2016 presidential race is trade. And for that, we have President Barack Obama to thank.

It’s true that a monumentally successful president can set the international agenda. By the time Ronald Reagan left office, for example, the Soviet Union was on its way into the dustbin of history. But most presidents aren’t that successful. For them, failure often sets the agenda more effectively.

That’s because success creates opportunities that didn’t exist. Failure, on the other hand, limits opportunities. It shrinks the road, sometimes to the point that the next president can’t deviate too far, or too fast, from the path laid out beneath his feet.

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That’s what Obama has achieved. By dithering his way through the Syria crisis, he destroyed any chance that we might support a moderate opposition. We’ve been left, as the cliché goes, with no good options. So he’s set the agenda.

Or take defense spending. It’s now lower, as a share of our gross national product, than it’s been since the defense-starved late 1990s. And it’s likely to continue to drop, both because of the Budget Control Act, or automatic sequestration, and pressure from entitlement spending.

But even if, like me, you want to raise defense spending, there’s a limit to how much money the armed forces can usefully consume at the start of a buildup. So here, too, Obama set the agenda — both by weakening our forces, and by making it harder to grow them.

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And then there’s Iran. The nuclear deal is a bad one in part because the sanctions system that hurt the Iranian regime is collapsing. Sanctions aren’t like the barrier to a parking garage that swings easily up and down. They’re more like a medieval cathedral: They take decades to build.

Already, the Italians are so eager for Iranian business that they’re covering up their naked statues to avoid offending Iranian fanatics visiting Italy. There’s little chance the United States can recreate an international sanctions regime to enforce the deal. Again, Obama set the agenda.

So while there is plenty to dislike about Obama’s foreign policy, his failures make it harder for 2016 candidates to move far, at least in a first term, from his policies. It’s not about turning to old options; it’s about coming up with new ones.

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Of course, a major terrorist attack would focus our attention on security issues. But right now, the most controversial aspect of foreign affairs might be trade, because Obama’s record there is more ambiguous. As a result, we have more options open to us.

Apart from the free trade deals with South Korea, Panama, and Colombia negotiated by President George W. Bush and ratified in 2011, Obama’s claim to a trade legacy rests largely with the Trans-Pacific Partnership. This act, which features the United States and Japan as its biggest players, can be cut many ways. Some defend it as a free-trade agreement. Others see it as a corporatist giveaway at the expense of American workers, or as a regulator’s paradise. Yet others argue that it’s less about trade than it is about bolstering U.S. ties in the region.

Fairly or not, you can make the Pacific deal be about anything, from the administrative state to income inequality. Obama hoped the pact would be his legacy. But because he’s neither failed terribly nor succeeded wildly, he’s not set the agenda.

Politically, therefore, trade remains a useful issue — which is why it could be a defining one in 2016. . I hope the candidates remember that when it comes to trade, corporations and unions can both be special interests. The ones who matter are all of us: the American consumers.

Ted R. Bromund is a senior research fellow in The Heritage Foundation’s Thatcher Center for Freedom.