Mr. Trump also applied pressure to get the leaders of Israel, Bahrain and the United Arab Emirates to the White House for an agreement that many experts believe did little to realize the regional “comprehensive peace agreement” promised by the administration’s official National Security Strategy. Instead, the engagement offered little more than a photo opportunity to help Mr. Trump’s re-election and may have undermined future efforts to achieve lasting and meaningful results in the region.

Mr. Trump’s predecessors have also, on occasion, made decisions and deals that served their political interests. But those deals typically aligned with America’s stated policies and its interests. The problem is that too often Mr. Trump’s deals do not.

And that’s just the deals we know about: Few people have any real idea of what is being promised in other calls and meetings. We may never know. This inconsistent, incomplete and inscrutable patchwork of foreign policy is not just inefficient, it risks disastrous mistakes by the United States and miscalculation by allies and adversaries alike. It also provides a potential opportunity for the sort of ethical misconduct that worries many about the debts and dealings exposed in new reports about Mr. Trump’s taxes.

No one, not even Mr. Trump, can say with confidence what American foreign policy is on any given issue these days. Such uncertainty is a source of stress and friction, leaving American military personnel, diplomats and intelligence officers not only out of the loop but also out of step with each other and with allies. After almost four years of this uncertainty, foreign government representatives simply shortcut the system and look for a White House back channel to figure out if the United States will zig when it’s supposed to zag.

Even worse, the uncertainty means that Americans themselves cannot know, or trust, all the deals being made in their name. Although Mr. Trump will spend the remaining weeks of the campaign talking about some deals and denying others, the true extent of his corruption of American foreign policy will not be known for many years. As Americans go to the polls, they may not understand what each of Mr. Trump’s deals includes. But they should know how and why he’s making them.

If Mr. Trump manages to stay in the White House, he’ll believe he has a mandate for more of this kind of deal-making. Re-election will remove the last remaining guardrail against the corruption of American foreign policy and drive anyone who seeks to avert disaster underground or out of government. It’s impossible to predict the damage to America’s interests, power, credibility, relationships and reputation.

But there is one thing to trust: Over four more years, there is little Mr. Trump won’t deal away.

Alexander Vindman (@AVindman), who served on the White House National Security Council until this winter, is a doctoral student at the Johns Hopkins University School of Advanced international Studies and a visiting fellow at the University of Pennsylvania’s Perry World House. John Gans (@johngansjr), the director of communications and research at the University of Pennsylvania’s Perry World House, is the author of “White House Warriors: How the National Security Council Transformed the American Way of War.”

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