The national outpouring of grief following the news that Senator John McCain died at the age of 81 is reflective of America’s admiration for a life lived in service to country. Professional cynics occasionally dismiss that kind of sentimentality as an outmoded artifact of a trite past, but the public has again proven the cynics wrong. There were, however, plenty who abandoned taste, class, and perspective to register their persistent frustrations with John McCain, and we cannot say they are irrelevant. Foremost among these malcontents was the president of the United States.

Trump personally rejected a plan to issue a perfunctory statement praising McCain upon his death, the Washington Post reported. The president opted instead to issue a cursory 21-word tweet expressing “sympathies and respect” to McCain’s family. If the insult to the late senator’s memory wasn’t clear enough, the White House conspicuously abandoned tradition and raised flags over the White House to full staff following just over 24 hours of mourning. The animosity between these two men was mutual. For his part, McCain requested that both George W. Bush and Barack Obama, two men who bested him in pursuit of the presidency, deliver eulogies at his funeral. Donald Trump was not invited.

Many described these displays of hostility as “petty,” but they are anything but. This bitterness is emblematic of a contest of ideas and comportment. It’s a contest in which Trump and McCain competed and it’s still being waged on America’s political battlefields. The stakes could not be higher.

The contours of this fight were evident by the middle of 2015. John McCain said that Trump had “fired up the crazies” by advancing the unsupported idea that America’s illegal immigrant population was disproportionately violent and dangerous. Trump famously responded by saying that McCain was no war hero (a claim he’s been making for nearly two decades), and implied that spending five years in North Vietnamese captivity was a mark of shame. Camps formed quickly. Republicans such as Scott Walker, Lindsey Graham, and Rick Perry condemned Trump. The GOP’s influential entertainers defended him. Ted Cruz took both sides of the issue.

This was more than an internecine squabble about civility in politics. In fact, it was several things at once: a proxy fight over immigration policy; a contest to determine whether business interests or voters would enjoy primacy within the GOP coalition; a battle over whether policy expertise deserves to triumph over perception and sentiment; and, finally, a fight over character. Is the performative decorum displayed by conventional office-seekers a custom worth preserving? Or has “civility” become the shackles by which only conservatives ever seem to be bound?

These are weighty issues, and the arguments over them were never going to be resolved over the course of one election cycle. They are still being litigated just beneath the Republican Party’s surface.

Ultimately, though, the idea that will define John McCain’s career is likely to be the subject of even more scrutiny and consternation. It is the idea that America occupies an exceptional place in world history and that the responsibilities on its shoulders are commensurate with that extraordinary status.

“America has made a greater contribution than any other nation to an international order that has liberated more people from tyranny and poverty than ever before in history,” McCain said in one of his last speeches in the U.S. Senate. “We have been the greatest example, the greatest supporter and the greatest defender of that order.” Deeming the United States a “blessing to humanity,” McCain’s definition of the American mission in the world is a familiar one. It is not too terribly distinct from Ronald Reagan’s belief that the “responsibility for preserving the peace” is “a responsibility peculiar to our country . . . because we’re the only one that can do it.” This is, however, not Donald Trump’s vision for America’s foreign policy.

Trump’s ideal America is in retreat. It’s one of the few policy positions on which he has been consistent for decades. In the 1980s, he took out a $95,000 full-page ad in the New York Times questioning the value of America’s alliances. As a candidate, he repeatedly entertained abandoning an allied nation under attack by a hostile power. As president, he’s flattered aggressor states and disparaged their victims. Trump and his allies feign support for global free trade, but his fondness for tariffs and his ludicrous claim that America can return to an industrial age defined by “internal” competition betray his true beliefs.

Hostility toward American extroversion and the post-World War II order is as popular on the radical left as it is among the right’s reactionaries and isolationists. Like the president, some on the right can barely conceal their relief over the death of one of their staunchest ideological adversaries. That may be vitriolic, but it’s not petty. They have correctly assessed the value in defining McCain’s legacy in negative terms before the senator’s admirers have a chance to correct the record.

So many of the eulogies for Senator McCain have focused on his record of service to the nation both in and out of uniform. Few dwelled much on the ideas to which he devoted his public life. The idea that America is a “beacon of liberty and defender of the dignity of all human beings and their right to freedom and equal justice” is not universally cherished. Many would like to see the United States abandon that self-conception. America’s commitment to the ideals that McCain endorsed will be tested again.

One day, there will be an unforeseen crisis. On that day, those who call themselves nationalists will argue that the only proper response is retrenchment and appeasement. They will claim that the United States shares no common bonds with the human family and that American exceptionalism can be preserved only by turning our backs on a troubled world. When that day comes, John McCain will not be there to remind Americans of history’s lessons. That responsibility falls on us now.