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