J OE BIDEN was first off a flight from Burlington to Philadelphia the other day. Lexington was second, which afforded him a rare moment to observe the former vice-president in the solitude of an empty jetway. Perhaps Mr Biden knew he was being spied on. Perhaps he always expects to be, after half a century in frontline politics. Even so, to watch the stiff-legged 76-year-old stoop to pick up someone’s empty soda bottle and transport it, softly tutting to himself, to the nearest rubbish bin was to glimpse a modesty and diligence not obvious in American government these days.

His reputation for being a good guy has helped make “Uncle Joe” a hugely popular figure on the left. Recent polls make him the favourite for the next Democratic presidential ticket. The latest for CNN gives him 30% of the Democratic vote, with his closest rival, Senator Bernie Sanders, trailing on 14%. Mr Biden, who had been speaking in Burlington on a book he published last year, “Promise Me, Dad”, says he will decide whether to embark on his third run for president over Christmas. Having visited 31 states this year, he is clearly tempted to. It would be a mistake if he did.

That is not to underestimate his strengths, which go beyond amiability. As he demonstrated in Burlington, Mr Biden is a polished turn, with moderate instincts and an impressive history of courage in adversity. Newly elected to the Senate by Delaware, aged 29, he suffered the death of his wife and baby daughter in a car crash, leaving him with two young sons to care for. The eldest, Beau, a former attorney-general of Delaware with his father’s features and easy charm, died of brain cancer in 2015 aged 46. That deterred Mr Biden, in the depths of his grief, from running in 2016—as he explains movingly in his book, which is part-memoir for a beloved son, part-campaign tome.

He was also dissuaded by Barack Obama, who believed his deputy could not beat Hillary Clinton in the primary. He might have been wrong, especially if Mr Biden had entered the race before Mr Sanders began kicking up a storm. And he could certainly have beaten Donald Trump. Trading on his working-class roots and strong ties to labour unions, Mr Biden performs best in the post-industrial states, such as his native Pennsylvania, that swung the election for Mr Trump. He would also have presented a less easy target for the hard-right media than Mrs Clinton was.

But that was then, and now Mr Biden seems too old. His supporters say his faculties are as sharp as ever. But his audiences would be as likely to remember him as the Democrat vying to be the oldest man ever elected president. “He’s much older than I thought he’d be,” murmured the woman seated behind your columnist in Burlington, as the final applause faded away. Mr Trump and Mr Sanders, the standout performers of 2016, were also old. Yet the fact that they were politically unknown to most people mitigated the effect of that. Mr Sanders’s largely unproductive Senate career also meant he had few political skeletons to hurt him in the primary; unlike Mr Biden, who voted for many things during his decades in Congress that he would be forced to account for. The lesson of the past two presidential elections is that voters want the most novel candidate available to them. This suggests that Mr Biden’s current strength, his superior name recognition, would be a weakness.

Even in the flush of youth, in all truth, he was a lousy presidential candidate. His first run, in 1988 (the year before the Democrats’ youngest incoming House member, Alexandria Ocasio-Cortez, was born) started weakly and fizzled quickly after he was caught plagiarising a speech by Neil Kinnock, a British politician. His second, in 2008, went the same way, after several gaffes, including his description of Mr Obama, his then rival, as unusually “bright and clean” for a black candidate. There is a post-Trump view that Mr Biden’s foot-in-mouth propensity would come over as authentic and engaging. Yet his infelicities too often revive racial and gender stereotypes that no Democrat could get away with, let alone an old white male one. Mr Biden’s tactility could be a similar problem. After a welcoming hug from the vice-president, the elderly mother of one of his then colleagues told him: “No man has touched me like that apart from your father!” Though he has never been accused of anything untoward, Mr Biden’s notion of personal space does not accord with contemporary standards.

His top billing today probably says less about him than the Democrats’ backward-looking frame of mind. Mr Biden represents a lifeline to the golden days of the Obama administration; the biggest cheers in Burlington came when he mentioned Mr Obama. It is even possible to read his book, of real-life grief and recovery, as a political allegory for the erasing of the Trump blot that Democrats dream of. The fact that Mr Biden’s strengths, his conviviality and appeal to blue-collar voters, map Mrs Clinton’s big weaknesses reinforces the sense that his prominence is about the past, not the future. And elections are the other way round.

There is more than Mr Biden’s dignity at stake in this. The tremendous moral courage he has shown, in circumstances that every parent dreads, should resonate far beyond politics. It would be a shame to see it reduced to a footnote in a fiercely contested primary battle that he seems unlikely to win. That would also be a waste of Mr Biden’s potential to act as a Democratic elder statesman, unifying the party’s diverse candidates and parts.

Back to the future

Meanwhile, his prominence in the primary speculation is a barrier to progress. That is most obviously because the left has fresher, potentially better, working-class champions, who would be likelier to run if Mr Biden does not. Senator Sherrod Brown of Ohio is one. More broadly, it is unwise to think that Mr Biden’s long-ago working-class roots are a substitute for the serious reappraisal of economic policy that the Trump insurgency makes urgent. Democrats need new blood. They also need new ideas. The admirable Mr Biden offers neither.