The administration has twice reluctantly certified Iran’s compliance and is required to revisit the issue again next month. Ms. Haley said she doesn’t know what Mr. Trump’s decision will be. The International Atomic Energy Agency, which put unprecedented strong procedures in place for monitoring Iran’s activities, has repeatedly judged that Iran is fulfilling its obligations. In July, Gen. Paul Selva of the Air Force, vice chairman of the Joint Chiefs of Staff, told Congress that based on evidence submitted to intelligence agencies, “it appears that Iran is in compliance.”

Mr. Trump, however, has reportedly kept pushing his advisers to find a way out, and Ms. Haley appears to have answered the call. The essence of her case, presented Tuesday to the American Enterprise Institute, a conservative think tank, is that technical compliance with the nuclear-related commitments is not sufficient and that the president “has grounds” to declare that Iran is not fulfilling the agreement because of other destabilizing or objectionable behavior, like its ballistic missile tests, support for Hezbollah and hostility toward the United States.

“We must consider the whole jigsaw puzzle,” she said, “not just one of its pieces.”

She’s wrong. While Iran indeed is engaging in some very worrisome pursuits, the deal is confined to the nuclear program. As long as Tehran is staying within those limits, Mr. Trump has no reason not to certify compliance. The United States and its partners need to find other ways, including sanctions already in place and dialogue, to mitigate Iran’s other behavior. In the national interest, Washington has often held its nose and dealt with aggressive or unsavory governments, among them the Soviet Union, Russia, Pakistan and Egypt.

Ms. Haley misleads further when she argues that it would not constitute an American withdrawal from the deal if Mr. Trump didn’t certify Iranian compliance. That kind of spin will convince no one, and it won’t protect Mr. Trump for being blamed for whatever follows, including outrage from France, Britain, Germany, Russia and China, which are also parties to the agreement.

Ms. Haley’s scheme would also allow Mr. Trump to punt the deal’s fate to Congress, further distancing himself from responsibility. Under American law, failure to issue the certification would open the door for Congress to reimpose sanctions on Iran. Would it be so irresponsible? Congress overwhelmingly opposed the deal when it was negotiated, but many critics now see its value. In any case, lawmakers must demand concrete evidence of Iranian noncompliance, if there is any, before reimposing sanctions.