None of us can choose how we are remembered. Most of us are not remembered at all. Senator John McCain knows that he will be remembered. He faces a choice about how his remarkable career will be noted in its autumnal phase.

McCain will of course be remembered most of all for his service, and sacrifice and bravery, as a naval aviator and then as prisoner of war in Vietnam. He should also be known for his efforts in his early days in politics to heal divisions within the United States over the Vietnam war, and then between Vietnam and the United States.

In the world of politics he is known and will probably be remembered as a steadfast personal friend, despite disagreements of party. Michael Lewis’s remarkable tale of McCain’s loyalty to the disabled and mostly forgotten one-time liberal champion Morris Udall is, well, an unforgettable example. More than most politicians, McCain has had dramatic moments of principle-above-party high-road stands, as when he told a Republican questioner that she should stop suggesting that his then-opponent for the presidency, Barack Obama, was “an Arab.” As Colin Powell later pointed out, McCain’s response fell an inch short of perfection, in that he answered the questioner by saying that Obama wasn’t “an Arab—he’s a decent family man.” Still, in real time and near the end of a bitter campaign it was brave, right, to his credit—and in character.

John McCain knows that he will also be remembered for having lost that race, and having lost his cool by “suspending” his campaign (while trailing in the polls) supposedly to concentrate on the financial emergency, and of course for steering American politics down the path that led to Donald Trump by choosing Sarah Palin as his running mate.

These are all things he has done, choices he has already made, which still net out very strongly on the positive and admirable side. But there is another important choice he faces, days after being diagnosed at age 80 with the same form of aggressive brain cancer that within a year of diagnosis killed his friend and former colleague Edward Kennedy. This is a choice that will affect the way this chapter of his career is noted and his career as a whole.

As he makes this decision, he should consider Clair Engle.

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Few of today’s politicians or political writers have even heard of Clair Engle. I had to learn his name, in grade school civics courses in California, because he was one of our state’s two U.S. senators. (No one will remember the other: Thomas Kuchel, pronounced keekle, a Republican who succeeded none other than Richard Nixon as senator when Nixon became vice president under Dwight Eisenhower.) Engle was a Democrat, who when elected in 1958 took a seat that Republicans had held since 1890s. While in office he was known mainly for supporting California-related public works programs, and for flying his own airplane all around to see constituents, including through the vast, rural Second District that made up most of the northern part of the state and that he had represented as a congressman.

Then in the summer of 1963, when Clair Engle was 51 years old, a generation younger than John McCain today, he was diagnosed with a brain tumor, and underwent surgery. Within six months, he was partially paralyzed and unable to speak. Within a year of his diagnosis, in the summer of 1964, he was dead, at age 52.

But in those final few months, Clair Engle chose to do something remarkable—in fact the main thing for which he is now known.

In the spring and summer of 1964, soon after John Kennedy’s assassination and also the Birmingham Church bombing that gave new urgency to Martin Luther King Jr.’s leadership of the civil-rights movement, the Congress was considering what became the Civil Rights Act of 1964.

Southern senators led by then-Democrat Strom Thurmond were filibustering the bill. In those days, filibusters were real, with senators orating for hours on the floor, and it took a two-thirds vote, or 67 senators, to break them. By the time of the crucial cloture vote on June 10, 1964, Clair Engle was too sick to stand or speak, and he was in his final weeks of life. But he was brought to the Senate floor, and when the clerk read his name, “Mr. Engle—Yay or Nay,” to see whether he would vote in favor of cloture, Clair Engle lifted his hand toward his eye, signaling an “Aye” vote. He voted to end the filibuster and enact the historic civil-rights bill.

As it happened, and as with John McCain’s “decent family man” comment, this was one inch away from dramatic perfection. It turned out that Clair Engle did not “need” to come to the floor to cast that vote (although Engle may not have known that beforehand). Seventy-one senators supported an end to Strom Thurmond’s filibuster, so the bipartisan non-Southern bloc supporting the bill could have done without him. But Clair Engle, although he could not stand, wanted to take a stand, and did. And if he is remembered, this will be the reason why.

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Now John McCain is reportedly considering whether to come to the floor to cast his vote, on the Senate’s unconscionably rushed health-care bill. He is not as sick as Clair Engle was, but like Engle he would have every medical excuse, if he chose, to stay away. And while Engle overruled his physicians to be part of a deliberation he thought history would respect, McCain is considering participating in a process that is the opposite of the best things he has stood for in his career.

John McCain at his finest has been an understanding, non-ideological figure. Yet he is considering lending his support to a bill whose only stated rationale is a need for a partisan “win.”

McCain at his best has been devoted to the long-term welfare of American institutions and governance. Yet he is considering showing up to support a bill no one has read and whose contents not even its partisans can describe (because they had not been set), and whose process violates every deliberative norm of the Senate.

McCain is even now the beneficiary of the most expert health care the United States can provide, with coverage due to him as a veteran and as a member of the Senate. And his doctors may certify that he is strong and robust enough to travel across the country and vote to take medical protections away from tens of millions of his fellow citizens. It’s almost too obvious a contrast to mention—but it’s one that the best John McCain must recognize, and that his biographers certainly will.

John McCain does not need to do this. He doesn’t have to worry about facing a Republican primary challenger in Arizona ever again. And anyway, the health-care repeal is as unpopular in his own state as it is everywhere else. What does a man with his record of service owe Mitch McConnell? Or Donald Trump? The same Trump who ridiculed him as a loser, for being captured in Vietnam?

What does John McCain have to lose, by doing what he knows is the right thing? What might he gain, by setting an example for other Republicans who know that Trump and McConnell are marching them toward shame and folly?

John McCain has long taken pride in his identity as “maverick.” This is his chance to cement the good side of that reputation, or lastingly compromise it with a step similar to his choice of Sarah Palin. If he votes for this bill, he will deserve all the opprobrium that follows.

Clair Engle’s most bravely memorable moment as a legislator was his last, when he voted: Yes. Of course I hope the vote this week will be very far from John McCain’s last. But he will be remembered for this vote, and I hope the memory is of him voting No.