The 60-day negotiating period established by the Memorandum of Understanding between the United States and Iran expired this week without a final agreement. What does that mean from a national security standpoint, and what are the domestic political implications?

From a national security perspective, the Iranian regime has been significantly degraded, but, as evidenced by the continuing crisis in the Strait of Hormuz, it has not been neutralized. And until proven otherwise, its nuclear ambitions remain a threat.

Public polling consistently shows that while Americans care about foreign policy, they rarely vote primarily on foreign-policy issues. Instead, they tend to evaluate events abroad by their impact on America’s security and prosperity at home. The economy, inflation, immigration, and other domestic concerns remain the dominant drivers of voting behavior.

In other words, foreign policy becomes domestic policy when Americans begin paying the price for it.

That may help explain President Trump’s job approval, now at the lowest level of his presidency. Rising inflation and energy costs certainly matter, but I suggest there is something else in the equation: Americans are losing confidence that the conflict with Iran is moving toward a successful conclusion.

In their influential book, “Paying the Human Costs of War,” Christopher Gelpi, Peter Feaver, and Jason Reifler argue that one of the most important factors shaping public support for military conflict is the expectation of success. If Americans believe a conflict will achieve its objectives, they can tolerate substantial costs. When they conclude the mission is unlikely to succeed, support erodes, even when the costs are comparatively low.

That is the danger facing the administration.

Americans can accept sacrifice when they understand the objective and see measurable progress toward it. What is much harder to sustain is sacrifice without a clear sense of when, or how, the conflict will end. Prolonged uncertainty begins to look less like strategy and more like stalemate.

Repeated promises to cripple the “Death to America, Death to Israel” regime, only to follow those threats with renewed invitations to the negotiating table, appear neither to have deterred Tehran nor convinced Americans that success is approaching.

President Trump now faces a choice. He can allow this cycle of confrontation, negotiation, and escalation to continue, or bring the conflict to a decisive conclusion.

The Iranian regime and its malignant ideology have repeatedly demonstrated their resistance to diplomacy as well as political and economic pressure. If the objectives, as initially stated, are to permanently end Iran’s pursuit of nuclear capability and remove the threat the regime poses to its own people, the region, and ultimately the United States, then the administration must pursue a policy capable of achieving those objectives while recognizing the political limits of a protracted conflict.

An unresolved conflict carries consequences far beyond the Middle East. Every disruption in the Strait of Hormuz, every increase at the gas pump, and every new round of fighting brings a distant conflict closer to the American kitchen table.

And that is where foreign policy becomes domestic politics.

American elections are usually decided by what happens at home. But history often pivots on events beyond our borders, and sometimes those events determine what happens at home.

This article originally appeared here.