“That man is like superhuman,” Joy Manbeck told The New York Times at the annual People’s Summit in Chicago earlier this month. “He still plays basketball. He walks to work. I don’t care. I want him. Period. I want Bernie.” So does RoseAnn DeMoro, the indefatigable leader of the National Nurses United union. In an interview with McClatchy, she said the Vermont senator is “so clearly ahead” of other potential contenders in the nascent 2020 Democratic presidential field. She added, “He has the most comprehensive program. He’s been doing this his whole life. What people want is what Bernie is saying.”

She has a point. An April Harvard-Harris survey revealed that Sanders is the most popular politician in the country: 80 percent of registered Democrats and 57 percent of voters overall say they approve of him. During the 2016 primary, Sanders won key states that Hillary Clinton later lost to Donald Trump; her defeat was at least partly attributable to an “enthusiasm gap” among expected Democratic voters. Sanders himself has not indicated that he’s planning another White House run, but thanks to his popularity and the unexpected viability of his primary campaign, questions about his political future are being asked.

But all this speculation does prompt another, equally important, question: Should Sanders run? The answer is no, though not for the reasons his critics think.

The imprudence of a Sanders run has nothing to do with his status as an independent. Nor does it have anything to do with the other criticisms his opponents tend to lob in his direction. He did not cost Clinton the election; her loss can be attributed to myriad campaign failures, Russian interference, voter disenfranchisement, and the infamous Comey letter. He is not working at cross purposes with the Democratic Party; he has in fact campaigned for the party’s candidates at its request and in fulfillment of his role as the party’s outreach chair. He and his followers do not represent some existential threat to the party’s identity; any winning Democratic coalition will need their numbers and energy, and as such it should reflect their policy preferences.

Still, there is a strong case for Sanders abstaining from making another presidential run. The first obstacle is obvious: He will be 79 next Inauguration Day. Basketball notwithstanding, advanced age is a vulnerability for any politician. This is particularly true of a politician who inhabits the Oval Office—and this critique applies to Joe Biden and other potential contenders of a certain age.

Second, while Sanders’s campaign ignited public interest in democratic socialism, he was hardly the perfect candidate. He could have been stronger on gun control, particularly at the beginning of the primary campaign. And he too often ceded ground on foreign policy to Clinton—an unnecessary failing, considering her deeply troubling record on the issue. These are questions that Sanders will have to answer all over again if he chooses to run in 2020, and they’re a reminder that there may be a better progressive candidate out there.

And there is the matter of his fame. Name recognition is key to victory, but it can also strangle movements. Sanders the individual now gobbles up so much airtime and column inches that he threatens to eclipse the American left, to its long-term detriment. This is hardly his fault, but Sanders must now consider the broader interests of the left.

Sanders’s candidacy served as catalyst for a surge of positive activity across the left. Interest swells the ranks of groups like Democratic Socialists of America, which existed before Sanders ran for president and will hopefully outlast his career. It propels Our Revolution, which emerged from the ashes of his campaign to elect progressive candidates. Though Our Revolution’s results have been mixed, it’s the sort of political infrastructure that must exist to support candidates who are otherwise ignored by the Democratic Party.

If this resurgent left is to survive and flourish, it needs to prove that it can work without a personality to prop it up. This won’t be news to longtime activists on the left, who organize mostly in obscurity on behalf of a constellation of progressive causes. It won’t be news to Sanders either, who was an activist long before he was a politician. For others, though, it may be more difficult to accept. Sanders’s candidacy energized a new generation of young voters, and he is now a celebrity. It is much easier to be publicly socialist now than it has been in decades, and this is a credit to the Sanders campaign.

But celebrity is a double-edged sword for any grassroots movement. Barack Obama’s Organizing for America withered without Obama’s involvement. The Clinton campaign also serves as a warning in this respect: Party leadership rolled Clinton out almost as if she were a product and urged voters to be “with her” rather than with any political philosophy or mission, as if her name alone implied a set of positive characteristics. Clearly, this was not enough to help Clinton last November. It may have even helped her lose the election.

Sanders, in contrast, had no national name recognition when he launched his campaign. He first became popular because of his policies; the persona followed later. It is now undeniable that his public personality currently rivals that of Clinton. His fame presents him with a singular challenge. If he were to run again, he would be synonymous with the left. If he abstains from another run, he’d highlight a key difference between left and center: For leftists, politics is based on policy, not personality.

Here, Sanders backers can learn from their British peers. As Sanders noted in a recent op-ed for The New York Times, Jeremy Corbyn’s Labour Party made up massive deficits when it released a positive manifesto that articulated a clear, concise anti-austerity message. Though Corbyn is the leader of the party and therefore its prospective prime minister, it seems to have been the manifesto, along with some serious policy missteps by Prime Minister Theresa May, that attracted defectors from parties on the right. And the party’s ads consistently reinforced a substantive political message: Vote for Labour because it is for the many, not the few.

This tactic led to huge gains. Post-election polls show Labour with a five-point lead over the Tories. Corbyn’s humane reaction to the Grenfell Tower tragedy has only sharpened the distinctions between Labour and the Tories, to the detriment of the Tories. Labour membership is growing, and the party is in excellent position to make a bid to reclaim government. This is partly because Corbyn directed party energy to building a movement centered on policy.

The popularity of Labour’s manifesto suggests an ideal role for Sanders. And he seems eager enough to embrace it: “While Democrats should appeal to moderate Republicans who are disgusted with the Trump presidency, too many in our party cling to an overly cautious, centrist ideology,” he wrote in his Times op-ed. The American left needs Sanders to help build a movement, and as a Senate ally to the progressive government we will hopefully elect. It needs him to shape the Democratic Party’s aspirations, to help demand a $15 minimum wage, Medicare for all, and free public college. Sanders can play a historically important role by mainstreaming these policies. Handing leadership off to another, younger progressive would be a sign of confidence in the party’s willingness to move left.

But there’s an important exception here. If there is no clear progressive frontrunnerno promising campaign for him to prop upSanders should run regardless of age. He’ll have a better shot at victory than he did in 2016, and after four years of Donald Trump, the country will need genuine progressive policies even more desperately than it does now.

Barring this scenario, Sanders should let another progressive run and embrace a movement-building role. In this capacity his age would become a boon, a testament to his long and often unrewarded dedication to a broader cause.