Four years ago Mitt Romney became a global laughing stock when he talked proudly about “binders full of women”. It was a funny phrase, no doubt about it. But watch the clip now, and it’s hard not to feel sympathy for the hapless Romney. He was recalling his spell as governor of Massachusetts and his discovery on taking office that too many senior posts were filled by men. He told his aides to encourage more female applicants, and they duly returned with “binders full of women”, a move that eventually led Romney to have the most gender-balanced senior team of all 50 US state governors. But he worded it badly, so he became an object of derision.

How long ago that seems now. While the 2012 campaign’s idea of a sexist outrage was a poor turn of phrase hinting at tokenism and condescension, 2016 has seen the nominee of a major party exposed as a perpetrator of sexual assault. Recorded on tape admitting that his modus operandi is to force himself on women, push his tongue down their throats without their consent and to “grab them by the pussy”, Donald Trump has since been confronted by at least 10 women who have testified that this was indeed his method – and that what he said into that hot mic in 2005 was the truth.

But we didn’t need to hear that recording to know Trump is an aggressive misogynist. His serial outrages are well known.He has called women dogs and pigs; he humiliated the winner of his Miss Universe beauty pageant for gaining weight, forcing her to exercise in front of the cameras; he rates women’s bodies out of 10; he dismissed Republican rival Carly Fiorina on the grounds that no one would vote for “that face”; he suggested TV anchor Megyn Kelly was hostile because “she had blood coming out of her wherever”. Even when seeking to rebut the charges of sexual assault, he couldn’t help himself. His defence amounted to: “Have you seen what these women look like? I don’t think so.”

This is such a swift degeneration from the public mores that America and the wider world had arrived at – and which had seemed steady and settled – that it can be hard to take in. It’s not that long ago that George W Bush received a global, and deserved, scolding for the unsolicited shoulder massage he fleetingly administered to Angela Merkel, which triggered a recoil reflex she could not conceal. Now you have a succession of credible accusers saying a would-be president thinks nothing of seizing women by the genitals.

As Michelle Obama put it in perhaps the most powerful speech of the presidential campaign: “We thought all of that was ancient history, didn’t we?”

Of course, that was a comforting delusion. You only have to read a fraction of the accusations of appalling sexual harassment and abuse of power levelled at Roger Ailes – the former overlord of Fox News, now reborn as an adviser to (who else?) Donald Trump – to know that such behaviour never stopped. Glance at the experiences shared online by EverydaySexism or under the notokay hashtag, and you know that men abusing women did not end in the 1970s.

Nevertheless the standard society set for itself aimed higher. Publicly, it deemed certain behaviour and attitudes unacceptable. Of course, the new standard was not always respected. But the line was drawn in a new place.

This is what Trump threatens. The way he both talks and acts seeks to roll back those 25 years of progress, sanctioning language and conduct that many had hoped was banished. The hope is that, if the polls are right and Trump is crushed next month, this will come to be seen as an aberration, allowing America to return to the more civil, more respectful habits it thought it had entrenched. The gloomier prospect is that the painstaking work of the last generation will have to be done all over again.

What’s more, this isn’t only about Trump. Fate conspired to pit perhaps the most misogynistic nominee in US history against the first female nominee. (Perhaps that’s no coincidence.) But even without Trump’s disgusting boorishness, the mere presence of Hillary Clinton’s name on the ballot may well have unleashed a torrent of misogyny. Witness the merchandise I saw on sale outside the Republican convention in Cleveland this summer. Among the slogans were: KFC Hillary Special: 2 fat thighs, 2 small breasts … left wing. Also: Hillary Sucks, But Not Like Monica. And the hardy perennial: Life’s a Bitch, Don’t Vote for One.

The intensity of this hatred can’t be explained solely by the controversies over Clinton’s emails, her hawkishness or links to Wall Street. More Americans have a “strongly unfavourable” view of Clinton than of any Democratic nominee since pollsters started asking the question. Some will say that’s because she’s a lacklustre campaigner. But compare her with, say, John Kerry, who was hardly electrifying on the stump in 2004. Among white men, 52% hold a “very unfavourable” view of her, compared with the 24% who took a similarly dim view of Kerry. It takes a wilful blindness to think this has nothing to do with the fact that Clinton is a woman.

In a fascinating essay for this month’s Atlantic, Peter Beinart surveyed the academic research that found men (and plenty of women) unnerved by women in traditionally male roles, especially overtly ambitious women, judging them more harshly than they would men. Roles don’t get much more traditionally male than the US presidency. What’s more, Beinart cites polling that shows Clinton has been at her most popular when “conforming to traditional gender roles (working on women’s issues as first lady, sticking by her husband during the Monica Lewinsky scandal, loyally serving Barack Obama as secretary of state), and least popular when violating them (heading the healthcare task force, serving in the Senate, running for president).”

The most obvious manifestation of this sexist hostility to Hillary is in the hatred spat out by Trump and his most devoted followers. But might some of that same sexism lurk in the now cliched insistence that she’s a terrible candidate, that Trump v Clinton is like choosing between cholera and gonorrhea, as Julian Assange memorably put it, that progressives can only vote for her while holding their nose?

Michelle Obama was right: no candidate in the modern era has ever been more qualified. Clinton won all three debates by outwitting Trump, luring him into one trap after another. She is serious, sober, prepared and with a detailed grasp of policy. And, despite Trump’s taunts to the contrary, she has demonstrated extraordinary stamina. Yet somehow, for some, she’s still not quite good enough.

The optimistic view is that the best remedy for this strain of sexism is simply for America to see a woman in the White House and get used to it. But the depressing evidence of the last eight years is that racial resentment actually rose rather than fell while Obama was in the Oval Office. It suggests that neither electing Clinton nor defeating Trump will be enough to defeat the demons unleashed by this campaign. That work won’t end on 8 November. It will begin.

• This article was amended on 26 October 2016 to correct the spelling of Carly Fiorina’s first name.

