Earlier today, the United Nations General Assembly condemned President Trump’s Dec. 6 decision to recognize Jerusalem as the capital of Israel. This follows on the heels of Palestinian Authority President Mahmoud Abbas’s declaration that “the United States has chosen to lose its qualification as a mediator” in the Israeli-Palestinian peace process. Insofar as a mediator requires both parties to accept its authority, the U.S. has reached the end of its ability to mediate the peace process between Israel and the Palestinian Authority.

Trump claimed that declaring Jerusalem to be the capital of Israel was “nothing more, or less, than a recognition of reality,” which, he speculated, would better facilitate negotiations between Israel and the Palestinian Authority. In fact, Trump’s declaration and its fallout reveal how the U.S.’s role as mediator since the 1970s has always rested on shaky foundations. That’s because the U.S., despite official claims, has rarely considered Arab-Israeli peace a vital interest. Trump’s actions bring this reality out into the open, which may be a more substantial, if unintended, contribution than the U.S. declaration.

After the U.N. vote to partition Palestine in 1947, the United Nations, not the United States, played the primary mediating role between Israel and the Arab States (Arabs did not recognize an official Palestinian body until 1964, and the Palestinian Authority was not created until 1994). But over the next 25 years, four regional wars broke out and despite its efforts, the U.N. failed to stunt the consistent outbreak of violence or move the parties toward peace negotiations.

After 1973, the U.S. took an increasingly prominent role in mediating the Arab-Israeli conflict as the region became central to U.S. interests and the U.N. lost credibility in the eyes of Israelis (and many Americans). More direct U.S. intervention created the precedents that influenced its future role as mediator. As secretary of state, Henry Kissinger embarked on his famous shuttle diplomacy, helping to forge cease-fire agreements between Israel and Arab states that would eventually lead to peace between Israel and Egypt and Israel and Jordan.

It was Jimmy Carter, however, who most solidified the role of the U.S. as mediator and established peace as a vital U.S. interest in the region. The 1978 Camp David Accords and the resulting Israeli-Egyptian peace produced three Nobel Peace Prizes and solidified Carter’s legacy as president. Carter used hard and soft U.S. influence at Camp David to leverage everything from threats to reassess U.S. diplomatic relations to massive U.S. aid packages, and set the model of presidential mediation that his successors have tried to duplicate.

Perhaps Carter’s most potent argument for U.S.-led mediation, however, was his claim that America’s chief interest was peace, and that it had a moral and strategic interest in securing this peace.

“The United States has had no choice but to be deeply concerned about the Middle East and to try to use our influence and our efforts to advance the cause of peace,” Carter argued to a joint session of Congress in 1978.

Peace was Carter’s priority and the pretext for U.S. mediation — not stability or the spread of democracy or the protection of economic interests. In Carter’s view, these were only achievable through peace. A devout Christian who ended his speech to Congress by reciting Jesus’ words — “Blessed are the peacemakers” — Carter was so committed to peace that the ultimate agreement he brokered with Egypt and Israel left unaddressed Palestinian statehood, refugee resettlement and the status of Jerusalem to close the “more than 2,000 years since there was peace between Egypt and a free Jewish nation.”

The Carter model — intense personal investment, aggressive demands of both parties, the promise of massive U.S. financial aid — succeeded in 1978, but its prioritization of peace did not last. Focusing on peace did not address other strategic interests in the region, including Cold War alliances and the U.S. need for cheap oil. In practice, both took priority over peace.

During Carter’s administration, developments in the Middle East also undermined his efforts. The Iranian Revolution in 1979 recast Middle East alliances and prompted Carter to declare his own “doctrine” in his final State of the Union address in January 1980: “An attempt by any outside force to gain control of the Persian Gulf region will be regarded as an assault on the vital interests of the United States of America.” In other words, vital interests besides peace were in play.

And yet the Carter ideal loomed large, and virtually all subsequent administrations have tried to re-create a Camp David breakthrough and play the role of peacemaker. Every president since Carter has reaffirmed the U.S.’s mediating role between Israel, the Arab states and the Palestinians, even as no administration has actually prioritized peace as the overriding U.S. interest. Individual diplomats, officials, and presidents have pursued new peace initiatives, but these have hardly defined U.S. policy in the region. The belated efforts by Ronald Reagan in 1988, George H.W. Bush in 1992 and Bill Clinton in 2000 are all cases in point.

The U.S.’s prioritization of peace has ebbed and flowed in the past 40 years. But its role as a pretext for U.S. mediation has collapsed since Trump took office in January. To everyone but the administration’s supporters, new levels of official U.S. identification with Israel and the decision to recognize Jerusalem have gutted America’s claim — rooted in Carter’s approach 40 years ago — that U.S. interest was best served by a solution to be decided upon by the principal parties with U.S. mediation.

The collapse of the U.S.’s mediating role could lead to positive developments. As American politics has polarized, and as support for Israel has increasingly divided along partisan lines, U.S. policy in the Middle East will continue to be shaped by domestic politics, even more than it already is. Removing the U.S. from primary mediation will remove peripheral interests from Israeli-Palestinian negotiations. At the same time, the close U.S. support for and cooperation with Israel could prioritize not a peace solution (which increasingly fades) but broader U.S. interests. Likewise, the U.S. could base support and aid to the Palestinian Authority on economic and political bench marks related not to Israeli concerns or the peace process, but according to broader U.S. interests in the region.

On the other hand, a future U.S. absence in Israeli-Palestinian negotiations could lead to even more dismal results than the past four decades have produced. U.S. influence and financial aid have kept both sides at least officially endorsing a two-state solution. In contrast to the era of U.N. mediation, there have been no regional scale wars in the Middle East since 1973. And it remains highly circumspect if the U.N. has the will, ability or credibility to mediate peace negotiations any better than the U.S.

The Trump administration’s recent decisions and the fallout are a departure from the U.S.’s historical position, but they also lay bare the awkward fit of U.S. mediation on an issue that has often been secondary to other U.S. interests in the Middle East. How Trump and future officials understand the U.S. role in the Middle East will depend on how seriously they consider peace between Israel and the Palestinians a vital American interest.