Elizabeth Warren was in New York this week, on the stump in front of large crowds in Washington Square Park. The contender for the Democratic party presidential nomination talked about corruption in the White House and the need for sweeping, dramatic change; she repeated her proposal, if elected, to impose a 2% tax on the country’s highest earners and she namechecked an early-20th-century labour movement spearheaded by women. After the rally, people stood in line for an hour to take photos with her. All of which invited only one possible response: I think Donald Trump’s going to win.

Electoral pessimism on the left in the United States is a finely balanced game that, depending on your view, acts either as a check to complacency or a self-defeating hedge that guarantees the very result it’s seeking to avoid. For many, predicting a second term for Trump goes back to the experience of watching George W Bush win a second election when John Kerry was a strong favourite. Hope is all well and good, but what about superstition?

The gravitational pull towards pessimism was impossible to resist

The difficulty comes, of course, when this gloominess infects the coverage of the candidates, giving rise to the sort of dithering analysis that seems to hand the other side ammunition. A New York Times article this week unpacked Warren’s “critical vulnerability” – too elite-seeming to the white working class – just as fellow contender Kamala Harris is deemed too mainstream for the far left, and Bernie Sanders too far left for the middle. The exception to this is Joe Biden who, while being a million times better than Trump, is so uninspiring a candidate, no one can even stir themselves to predict his defeat (oh, and Bill de Blasio of course, currently polling at 0%).

Do Trump campaigners do this? One suspects not. His own delusional self-confidence, rooted in a pathology that in other circumstances might require clinical intervention, is mistaken across large parts of the country for leadership. And while the support Trump enjoys from rank-and-file Republicans is a stain on the party that will never be removed, there is no arguing that it’s effective. “He’s going to win,” I said to a friend this week, and she fairly screamed at me across the table. “Don’t say that!” But the gravitational pull towards pessimism was impossible to resist.

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Writ large, the chicken-and-egg effect of this impulse is impossible to audit. But it seems fair to assume that the grain of truth out of which critiques of Trump’s opponents grow can, with enough anxious attention, shoot up into a fully blown narrative able to strangle a campaign from within, leaving Republicans to hold their noses and vote in Trump for a second term.

And so, while it may be true that Warren has a wonkish aspect that doesn’t play well with voters who didn’t go to Harvard, the real danger for her campaign lies elsewhere, in the bent-out-of-shape psychology of the left – anticipating defeat just to soften the blow, and muttering to ourselves, “No we can’t.”

• Emma Brockes is a Guardian columnist