It all started with a single tweet.

Outraged by Donald Trump's boasts about grabbing women's genitals and forcing himself on them, Canadian author Kelly Oxford urged her hundreds of thousands of followers to share their recollections of the first time they were sexually assaulted.

What she didn't expect was the seemingly unstoppable chain she set in motion, with more than a million women sharing their experiences, and with that placing an explosive subject front and center of the campaign to become America's next president.

A 39-year-old writer, Oxford launched the Twitter appeal within hours of Friday's release of a 2005 Trump video, using the same word that Republican presidential candidate Trump employed in the video.

"Women, tweet me your first assaults. They aren't just stats," she wrote.

Oxford then went first: "Old man on city bus grabs my 'pussy' and smiles at me, I'm 12."

A student carries around a sign on the campus of Washington University in St, Louis, Missouri where the second presidential debate took place. Photo: AFP

And with those words, the Los Angeles-based blogger became a major Internet celebrity.

Within an hour, she had already racked up thousands of witness accounts, with the hashtag #notokay taking social media by storm.

The next day, Oxford tweeted to express surprise at the rate of responses: around 50 per minute and well over a million at that point.

Most were women who, sometimes with modesty, at times in crude details, describe in several words how a parent, a friend of a friend, a professor or a stranger once abused them.

But joining the chorus were also some men who were either themselves victims of violence or sought to distance themselves from Trump's belligerent rhetoric and behavior.

Nearly five days on, the rhythm has slowed but the witness accounts keep pouring in.

While it is still too early to tell if Trump can scramble back up to the top of the polls after the hit he took following the revelations of his lewd, decade-old comments, the episode has reignited a fierce debate about sexual violence in the United States.

After dozens of Republican figureheads publicly withdrew their support from Trump, some of his backers dismissed the comments as simply "locker room talk."

'More awareness'

In 2015, views were similarly sharply divided when a then-student athlete of California's prestigious Stanford University, Brock Turner, was sentenced to just six months in prison after raping an intoxicated and unconscious 22-year-old woman during a fraternity party.

A petition with more than a million signatures asked that Superior Court Judge Michael Aaron Persky, himself a former captain of Stanford's lacrosse team, be recused from the case.

The scandal led to tighter anti-rape laws in California in September.

Terry O'Neill of the powerful National Organization for Women, recalled how another hashtag urging women to share their experiences of assault or discrimination -- #yesallwomen -- went viral in 2014 after Elliot Rodger went on a killing spree after women refused his advances.

And the sordid scandal that brought down former IMF chief Dominique Strauss-Kahn, who was accused of trying to rape a chambermaid in New York, had also triggered countless revelations by women who said they had suffered sexual assault or violence perpetrated by politicians.

"We really have made some progress, we have come a long way," said O'Neill.

"We may be at a moment where we expect real changes and really put an end to rape culture."

At least one in five people have been directly or indirectly affected by this type of violence in the United States.

"It's good that outrage is being voiced, it's creating more awareness... on a huge societal issue," said Delilah Rumburg, CEO of the National Sexual Violence Resource Center in Pennsylvania.

While doubting that these witness accounts will change the minds of people who plan to vote for Trump, Rumburg found it "very encouraging" that men are also participating in the debate by rejecting sexually predatory behavior.

"The more we talk about it, the less acceptable it is going to be," she said.

Jean Kilbourne, an author and speaker known for her work on the image of women in advertising, hailed the success of #notokay.

"For years, for a lot of us, we would tend to minimize it because the culture tends to minimize it, even though it has a lasting impact," Kilbourne said.

"It is just extremely important to realize how many women have had these experiences."

She then added, with a laugh: "Donald Trump has actually managed to bring a very serious issue in the campaign."