Why is it so hard to quit politics?

The Johnson Swan Song

After suffering a demoralizingly narrow (50 percent to 42 percent ) win over intra-party challenger Eugene McCarthy in the 1968 New Hampshire primary, Lyndon Baines Johnson realized that, given the unpopularity of the Vietnam War, an exceedingly rocky road lay ahead, both to his party’s nomination and to victory in November.

LBJ, however, didn’t say that when he bailed out just a few weeks later. He couched things this way: “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 your country. Accordingly, I shall not seek, and will not accept, the nomination of my party for another term as your president.”

Did LBJ fool anyone? Not really. But his focus-on-Vietnam rationale gave him a face-saving reason to step aside. Interestingly, that decision didn’t help his party. Back in the day when there were real power brokers and actual smoke-filled rooms rather than pledged delegates and no-smoking-anywhere arenas, party panjandrums then bestowed the nomination on Vice President Hubert Horatio Humphrey, who hadn’t entered a single primary. Adding to the atrocious optics: They did so while the Chicago police were busting the skulls of antiwar-protestors outside Chicago’s International Amphitheatre.

HHH never managed to put the Democratic Party fully back together, and with George Wallace running as that year’s southern resentment candidate, Republican Richard Nixon won in November.

The Tsongas Sidestep

Former US Senator Paul Tsongas left New Hampshire on the wings of victory in 1992, having scored a next-door-neighbor primary victory over one-time frontrunner Bill Clinton, then the governor of Arkansas who had been beset by — imagine! — controversy. But Tsongas, running on a platform of fiscal discipline and inter-generational responsibility, did not fare well when the nominating contests moved to the South and then the Midwest. Meanwhile, campaign money man Nick Rizzo had siphoned off a million or more in much-needed contributions.

Facing drained coffers and fading prospects, Tsongas concocted an inventive rationale for leaving the race: If he stayed in, his intergenerational exhortations would somehow be bruised and battered beyond recognition in campaign conflict.

“My message would have been wounded, and all that we worked for, for this past year, would have been put at risk,” he said. “The message must endure.”

Tsongas and former senator Warren Rudman of New Hampshire then formed the Concord Coalition, which still plays a role in advocating for fiscal discipline and against loading debt onto future voters.

The Mittski Quitski

When he decided not to seek what would have been a tough re-election as a US senator from Utah, Mitt Romney, the Republican Party’s 2012 presidential nominee, put a pass-the-torch spin on his announced exit.

“At the end of another term, I’d be in my mid-80s,” Romney said last September. “Frankly, it’s time for a new generation of leaders. They’re the ones that need to make the decisions that will shape the world they will be living in.”

This approach has a noble, self-effacing aspect about it. It’s one that others of Romney’s vintage should consider. But will they? Probably not. After all, it runs afoul of the linger-long-at-the-political-party ethos of the baby boomers, whose motto seems to be: We’ll go when we’re damn good and ready — or dead.

Crotchety Crockett and Tricky Dick

Some politicians have abandoned politics, or seemingly done so, with a curmudgeonly swipe at their enemies.

Having suffered a dispiriting loss of a Tennessee US House seat, ending an in-and-out-of-office congressional career that stretched from the mid-1820s to the mid-1830s, Davy Crockett exited the Volunteer State political stage with this farewell to his former constituents: “You may all go to hell, and I will go to Texas.” As those who remember the Alamo know, that decision came with problems all its own.

After Richard Nixon lost the presidency in 1960 and then a 1962 race for governor of California, he proclaimed that he was calling it quits with a swipe at the press.

“You don’t have Nixon to kick around anymore, because, gentlemen, this is my last press conference,” he declared.

Nixon may have meant that at the time, but the siren’s call of politics proved too strong. After lying low through the next presidential cycle, Nixon emerged as the party’s nominee in 1968, defeated Hubert Humphrey for the presidency, and won re-election in 1972. Then the Watergate scandal broke, giving him an opportunity to leave politics yet again, this time for good.

Family ties and alibis

Many an embattled politician or political appointee has opted out of a tenuous situation by citing obligations of family. This often seems neither sincere nor plausible, particularly when offered by a man engaged in a controversy occasioned by his cavalier attitude toward his family-making partner.

That said, it would work well for Biden. Known as a genuine family man, he is sincerely worried about his son Hunter, who has had drug and alcohol problems and has now been found guilty of federal felony gun charges. Add in this advantage: If he were no longer a candidate for re-election, Biden could pardon Hunter on his way out the White House door.

Verily and forsooth, what about the truth?

As this tour of the ta-ta horizon shows, if there are 50 ways to leave your lover, there are many ways to depart the stage. One could even be honest and say: “At 81, I’ve lost a step or two – and in today’s world, you need a younger, more vigorous president, one who can keep pace.”

People would admire the president for his frankness, my word as a Biden watcher, they would. Plus, that would have the twin virtues of being true and self-aware.

Translation: Don’t look for it to happen.

This column first appeared in The Primary Source, Globe Opinion’s free weekly newsletter about local and national politics. If you’d like to receive it in your inbox every Wednesday, sign up here.

Scot Lehigh is a Globe columnist. He can be reached at scot.lehigh@globe.com. Follow him @GlobeScotLehigh.