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.

* * *

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.