As Election Day neared, Democrats’ hopes soared. I know because I saw it and heard it all around me — the widening smiles, the brightening voices. Vice President Kamala Harris was ascendant. Donald Trump was done. People could just feel it.

They were reacting to polls, though they were picking and choosing: To listen to them, that outlier survey in Iowa, which augured a Harris victory in a red state that she ended up losing by about 13 percentage points, was some amalgam of the burning bush and the Rosetta stone.

They were reacting to “momentum,” which is a word as squishy as a wet paper towel and a concept beloved by dreamers whose yearning outstrips actual evidence.

But they were reacting above all to Trump. To how epically awful he was being. In his increasingly saturnine and serpentine remarks, he imagined Liz Cheney facing a fusillade of bullets, he called Democrats “demonic,” he said that he should never have left the White House after the 2020 election. All of this was characterized by many observers as the most self-destructive, disastrous conclusion to a presidential campaign that they’d ever beheld. And all of it was identified by the optimistic Democrats around me as the last straw.

Americans — at least the ones whose minds weren’t firmly made up — would surely abandon Trump now. There was a limit to the cruelness and craziness they’d abide.

That judgment, of course, was terribly wrong. And I want to name and dwell on a few of the reasons for its wrongness, because they’re stubborn misapprehensions, enduring blind spots. They’re costing Democrats — no, they’re costing America — dearly.