Since becoming president, Joe Biden has faced calls to step aside and not run for reelection out of concern that he’s too old for the job. And since his disastrous debate performance, those calls have only grown louder.

What might be making him press ahead? Some have suggested that the president feels an overwhelming sense of duty to serve his country and believes that stepping aside would be a cop-out. Others have theorized that he remains in the race because he thinks he’s one of the few people — if not the only one — who can beat Donald Trump. As Biden told supporters, “If Trump wasn’t running, I’m not sure I’d be running.”

In this case, it’s also hard to ignore the obvious: Power is an extraordinarily difficult thing to walk away from. Take it from a former president who voluntarily chose not to run for reelection.

“There is a lure in power,” Harry Truman wrote in 1950, two years before he publicly announced that he would not seek another term. “It can get into a man’s blood just as gambling and lust for money have been known to do.”

Power can distort someone’s view of reality, making them believe they’re invincible or somehow not bound by the basic rules of biology. But while that makes power all the more seductive, it’s not impossible to break its spell. After all, for well over a century before there were term limits, American presidents tended to know when to call it quits: If they weren’t killed or voted out, they voluntarily bowed out after serving two terms — that is, until Franklin Delano Roosevelt was elected in 1932 and won four consecutive terms.

Notably, two more recent presidents, Harry Truman and Lyndon B. Johnson, chose to walk away from the job. Here’s what we can learn from them.

If Biden were to drop out of the race, he wouldn’t be the first incumbent president to know when it’s time to go.

Truman, a Democrat, was the last president who could have run for as many terms as he would have liked; the 22nd Amendment, which put in place the presidential term limits we still have today, applied only to presidents who would go on to serve after him. Truman won only a single full term in office in 1948, but he had also served almost the entirety of FDR’s fourth term after Roosevelt’s death.

Truman had had his fill. “In my opinion eight years as President is enough and sometimes too much for any man to serve in that capacity,” he wrote. “When we forget the examples of such men as Washington, Jefferson and Andrew Jackson, all of whom could have had a continuation in the office, then will we start down the road to dictatorship and ruin.

“I know I could be elected again and continue to break the old precedent as it was broken by F.D.R.,” he continued. “It should not be done. That precedent should continue — not by a Constitutional amendment but by custom based on the honor of the man in the office.”

After facing several setbacks, including declining popularity and losing the New Hampshire primary, Truman announced in March 1952 that he wouldn’t seek reelection. The Democrats held a brokered convention later that year and ultimately picked Adlai Stevenson, then governor of Illinois, to be their presidential nominee. (Stevenson also happened to be Truman’s preferred candidate.)

In 1968, President Lyndon B. Johnson also chose not to seek reelection. Johnson’s administration had been mired in the Vietnam War, and he was quickly losing domestic political support. He was facing serious challengers in the Democratic primaries and realized that his road to reelection would be rocky. The Democratic Party also seemed split, with many preferring someone like Robert F. Kennedy to move the country forward. He also had concerns about his health, uncertain that he could live out another term in office.

So Johnson pivoted, focusing the remainder of his presidency on salvaging his legacy.

“With America’s sons in the fields far away, with America’s future under challenge right here at home, with our hopes and the world’s hopes for peace in the balance every day, I do not believe that I should devote an hour or a day of my time to any personal partisan causes or to any duties other than the awesome duties of this office — the presidency of this country,” Johnson said on March 31, 1968, when he announced he wouldn’t seek reelection. The party went on to nominate his vice president, Hubert Humphrey, as the next Democratic candidate for president.

Neither Johnson nor Truman can be considered wildly brave for their decisions. Both had tanking approval ratings, and for anyone watching, the writing was on the wall: Reelection was highly unlikely.

The outcomes of their decisions can be viewed in many different ways. Both Democratic presidents saw their party suffer crushing defeats after they withdrew from their race. Then again, who’s to say the elections would have been different if they’d stayed in?

But the fact that they knew when to quit was itself notable and worth commending. And as it turned out, both men saw a bounce in their approvals after withdrawing from the race.

Biden could well be thinking: If Johnson and Truman dropping out didn’t save the party’s chances, then should he follow in their footsteps? More than that, the post-presidency for Johnson led him to agony, depression, and self-pity — yet another personal reason Biden might want to plow through.

There’s more to Truman’s and Johnson’s stories, however, than the political outcomes that followed. The fact that they were able to walk away from the most powerful office in the country rather than being forced out was itself an admirable display of humility: a willingness to realize that there’s more to life than politics or their legacy.

There is no question that it’s not easy to leave the presidency behind. One of Johnson’s daughters told the former president’s biographer, historian Robert Dallek, that her father’s career was essentially his whole identity. “My daddy committed political suicide for that war in Vietnam,” she said. “And since politics was his life, it was like committing actual suicide.”

Johnson might have been angry on his way out of the White House, but he also looked forward to life on his Texas ranch without the burden of the presidency. “By God I’m going to do what I want to do,” he said. “If I want to drink a glass of whiskey, I’m going to drink a glass of whiskey. And if I want to have some bad manners, I’m going to have bad manners. I’ve got some freedom to do what I want to do.”

Truman likewise stepped into the post-presidency by looking forward. In his farewell address to the nation, he reflected on his years in politics with pride and appeared sure in his decision to step down. “So, as I empty the drawers of this desk, and as Mrs. Truman and I leave the White House, we have no regret,” he told the nation in January of 1953. “We feel we have done our best in the public service.”

At 81 years old, Biden has a lot to gain in his personal life from walking away. Past the average life expectancy of the average American man, he has the option to spend the rest of his time with friends and family, especially after a five-decade career in national politics.

Like any president, however, his chief concern seems to be his legacy, and he likely believes that sending his party to a loss in the fall could ruin it, whether he’s on the ticket or not.

Like Johnson and Truman, Biden has lost political support because of his involvement in a foreign war. But he’s also struggled with voters simply because of his age. After all, more panic set in among Democrats after Biden’s poor debate performance this week than during the campus protests on Gaza or the protest “uncommitted” campaigns during the Democratic primaries.

Though the polls at press time suggest that Biden is on track to lose in November, it’s certainly within the realm of possibility that Biden could eke out a victory because he’s running against a weak candidate with extraordinarily heavy baggage. It’s also possible that if Biden drops out, the Democratic candidate who replaces him will lose.

But if Trump defeats Biden, the postmortems will likely say that the writing was on the wall before the campaign even began and that Biden handed democracy to a would-be autocrat simply because he had too much pride to drop out.

Short of winning, there’s only one thing Biden can do to prevent his legacy from being defined by his ego: He could give someone else a chance.

Flawed as their tenures may have been, Johnson and Truman understood that the presidency isn’t theirs to keep, and that power, however alluring, is fleeting. Biden would be wise to remember that.