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Halfway through a Monday morning in August, three of Bernie Sanders’s top advisers led a conference call to complain to reporters covering the campaign about Sanders’s treatment in the political press. In 2016 there had been a “Bernie blackout,” said Jeff Weaver, the senator’s longest-serving aide and his campaign manager that year, repeating a frequent claim of that effort’s veterans that the candidate was insufficiently covered. Now they were looking at a “Bernie write-off,” Weaver said, wherein his chances weren’t being taken seriously enough, to the point where polls in which Sanders performed well were being effectively ignored. To the journalists on the call, and to some of Sanders’s political allies, it sounded like a familiar line of argument they’d likely hear plenty of over the ensuing half-year.

Four months later, though, Sanders is still far from the biggest national story, but his team has stopped this particular strain of griping. If the mainstream press was going to ignore him, after all, that probably meant their opponents were missing the story, too. And now, just weeks before Iowa’s caucuses and hours before the final primary debate of 2019, Sanders’s rivals are facing up to the fact that the man most of them long ago concluded was no real threat is still sitting in first or second in nationwide or early state polls, still potentially playing with more campaign cash than any of them, and still showing no signs of going anywhere.

That’s led some of them to a series of unexpectedly uncomfortable questions. To start: In all their confidence that he couldn’t win, did they miss a chance to take Sanders down at some point in the three years since 2016? And is there any way now to chip away at his apparently rock-solid base of support — which perhaps isn’t big enough to outright win, but is definitely big enough to matter immensely in such a messy race — without blowing themselves up?

Many Democrats, including powerful party figures aligned with the other major campaigns, don’t necessarily believe Sanders is well-positioned to win the nomination, but they acknowledge that his consistent backing of somewhere between 10 and 20 percent of the primary electorate will at least allow him to compete seriously well into next year.

Among this contingent, the thinking goes that since far from all of Sanders’s 2016 backers are with him this time, his floor and ceiling of support are close together, so he poses little threat over the contest’s long-run: “He basically has unlimited resources, he’s done this before, and he’s willing to play the long game,” acknowledged one longtime adviser to Joe Biden. But “can he grow the coalition that he had in 2016? I don’t know, at this point, there’s any evidence that he’s done that.” This idea has led most of them to conclude that attacking Sanders would ultimately be a waste of time — even if he sticks to the race far longer than they expected, especially after his heart attack this fall. (Sanders’s allies, meanwhile, know that his levels of support are nowhere near his 2016 numbers — when there were effectively two candidates in the race — but point to his far more diverse backing than last time as evidence that this claim from his opponents is wishful thinking.)

Even more important to the argument, though, is that national and early-state polling has shown little indication that many of Sanders’s existing supporters would be willing to back another candidate with the Vermonter still in the race. “So why piss off his people?,” wondered one veteran Democrat aligned with another candidate, concerned about potential backlash. “Why would I go there?”

But this theory of the case has created a race where three of the top four candidates — Biden, Elizabeth Warren, and Pete Buttigieg — have faced somewhat regular incoming from each other in the last few months, while Sanders has taken few direct hits from his serious rivals. While Buttigieg has positioned himself as a moderate warrior willing to actively criticize some progressive proposals — for example, running ads against Medicare for All and universal free public college — it’s only Warren who he’s been sparring with recently. He rarely, if ever, mentions Sanders, even if Sanders’s team shows no hesitance in criticizing him. Biden, too, rarely talks about Sanders. When the senator is mentioned, it’s often in tandem with Warren — seldom as a solo target.

Aides of other campaigns said that they’d attack Sanders if he was standing directly in their way. Instead, though, they say he so dominates his own lane in the race that the only candidate who could realistically try winning over his most loyal voters would be Warren.

Warren, however, has shown zero willingness to criticize Sanders, either, more than a year after they privately agreed not to go after each other on the campaign trail, and especially with two well-positioned moderates still opposing them in the race. Anyway, at this point she can little afford to risk antagonizing Sanders or his backers, who she believes she will ultimately need on her side to become the nominee. (The public comity has fueled some wishes from prominent progressives that the pair might link up on an eventual ticket, but this, for now, is fantasy: Warren and Sanders rarely speak, except when they run into each other while campaigning.)

For their part, Sanders’s campaign and its closest allies believe that it’s too late for any other candidate to have a reasonable shot at peeling off his core supporters as long as he’s running — “I don’t think they’re persuadable to go anywhere,” said Larry Cohen, the former Communications Workers of America union president who’s advised Sanders for years and now chairs the board of Our Revolution, the Sanders-aligned political group.

There was a moment when some of them could have made those inroads, he said, but it wasn’t other candidates’ hesitance to criticize Sanders that did them in, in his telling. It was their varying positions on Medicare for All that doomed them. “They gave that [opportunity] away,” he said. “They made a colossal mistake.”

To Establishment-minded Democrats concerned by Sanders’s staying power, then, it all adds up to an unsatisfying strategy of wait and hope. One senior Democratic strategist insisted to me that if it started to look like Sanders could actually win early next year, “It’ll be like, ‘Oh shit,’ and it’ll take care of itself.” The rest of the party, he said, would just coalesce behind another candidate. He just wasn’t sure which one.