The recent U.S.-North Korea summit in Hanoi has become the latest domestic partisan battlefield. President Trump now implies that congressional Democrats were at least partly responsible for the failure of negotiations with North Korean dictator Kim Jong-un. His allegations are exaggerated, but they are not entirely erroneous.

The summit ended abruptly without an agreement on any issue or even the publication of a joint communique. That outcome was a surprise to many experts. Widespread expectations existed that the two leaders would issue a declaration officially ending the Korean War, and that they would establish liaison offices as the first step toward full diplomatic relations. Optimists also hoped for an agreement on initial measures toward North Korea’s denuclearization in exchange for the lifting of some U.S. and international economic sanctions.

For days following the summit, the president insisted that the meeting had not been a failure, merely one step in a very long, difficult process. He also contended that it became necessary to walk away from the negotiations in Hanoi because Kim insisted on the lifting of all sanctions merely for closing the Yongbyon reactor complex—just one of North Korea’s known or suspected nuclear facilities. The North Korean government denied Trump’s version of events, insisting that their negotiators had sought only a partial lifting of sanctions for that concession.

In a March 3 tweet, though, Trump seemed to change his argument, attacking the Democrat-controlled House Oversight Committee for holding hearings featuring the president’s former personal attorney, Michael Cohen. Trump stated that the hearings were a nasty distraction that may have “contributed to the ‘walk.’” His revised explanation is unconvincing. As late as the weekend television talk shows, National Security Adviser John Bolton was still arguing that the cause of the summit breakdown was Kim’s excessive demand for sanctions relief. Yet when Trump issued his tweet on the afternoon of March 3, it somehow became the Democrats’ fault.

The administration’s handling of the summit warrants criticism. Preparations for those delicate, complex negotiations seemed inadequate, even slipshod. The apparent confusion about the nature and extent of North Korea’s position on sanctions especially suggests a lack of professionalism or even basic competence.

But congressional Democrats don’t deserve high marks for their behavior either. Some accusations in Trump’s March 3 tweet were justified. “For the Democrats to interview in open hearings a convicted liar & fraudster, at the same time as the very important Nuclear Summit with North Korea, is perhaps a new low in American politics.… Never done when a president is overseas. Shame!”

That is a valid point. The House Oversight Committee could have postponed those hearings until after the summit—indeed, it could have scheduled them for any other time. Choosing to hold inflammatory sessions on the same days when the president was conducting extremely sensitive negotiations with a difficult foreign power, involving matters of war and peace on the tense Korean Peninsula, was inexcusable. The timing raised understandable suspicions that Democrats were trying to undermine their political opponent—and the nation’s foreign policy—for partisan reasons. Their conduct was petty at best, and dangerously irresponsible at worst.

Moreover, that was not the extent of questionable behavior on the part of Democratic leaders in Congress. Nancy Pelosi, Chuck Schumer, and other senior Democrats spent the weeks before the summit making sneering comments that Trump might well “give away the store” to Kim in exchange for empty promises. Senator Robert Menendez (D‑N.J.), ranking Democrat on the Foreign Relations Committee, collaborated with hawkish Republican Senator Ted Cruz (R‑Texas) to oppose ongoing U.S.-South Korean efforts to create better relations with Pyongyang. Such unhelpful behavior caused even some on the left who seek to reduce the danger of war in Korea to accuse Democrats of sabotaging prospects for progress at the summit.

The partisan posturing before and after the Hanoi summit does little to alleviate the mounting public disenchantment with both major political parties. Neither Trump nor his opponents deserve even mediocre marks for their behavior. Especially on a matter that involved the challenge of preventing a possible war with nuclear implications, the American people deserved better.