It took barely four days for President Trump to go from describing Christine Blasey Ford as “a very credible witness” in the wake of her appearance before the Senate Judiciary Committee to savaging that testimony with a vicious rant Tuesday night at a political rally in Mississippi.

“ ‘I don’t know. I don’t know.’ ‘Upstairs? Downstairs? Where was it?’ ‘I don’t know. But I had one beer. That’s the only thing I remember,’ ” Trump said, mocking the gaps in Ford’s memory of the attack that she claims Supreme Court nominee Brett M. Kavanaugh made on her at a high school party as his friend Mark Judge cheered him on.

The hoots Trump drew from the crowd were a painful, ironic reminder of something Ford said she will never forget about that night: “Indelible in the hippocampus is the laughter — the uproarious laughter between the two and their having fun at my expense.”

At just about the same time Trump was shredding Ford in Mississippi, the 11 men who constitute the Republican majority on the Senate Judiciary Committee put out a statement that purported to describe the sexual preferences of Julie Swetnick, another woman who has accused Kavanaugh of misconduct in the 1980s.

The shameful move on the part of the Senate Republicans was as mystifying as it was unprecedented, given that Swetnick was already doing a pretty good job on her own of undermining the credibility of her allegations.

Swetnick’s story has shifted. She has yet to produce corroboration of a set of spectacularly horrifying accusations, including that Kavanaugh was present at numerous parties where gang rapes occurred. So why did the senators feel it necessary to add unverified recollections of something they heard from a man who says he had a brief relationship with her a quarter-century ago?

The answer from Kavanaugh’s defenders is that they are merely fighting fire with fire. But that is another way of acknowledging that what they really want is to turn back the clock.

Suddenly, the new rules of the #MeToo era are giving way to the old ones of the 1990s. Back then, women who had the temerity to come forward with allegations of sexual abuse against powerful figures would find that they themselves were the ones on trial.

After former Arkansas state employee Paula Jones claimed that then-Gov. Bill Clinton exposed his genitals to her in 1991, Clinton’s chief political strategist James Carville retorted: “If you drag a hundred-dollar bill through a trailer park, you never know what you’ll find.”

Republicans now cite that episode with regularity, of course, as almost every argument seems to wind its way at some point to, “What about the Clintons?”

But the real question should be: What have we learned since then?

One thing is that women who make these charges deserve a serious, respectful hearing. Another is that not every accusation is going to prove credible, or even produce any kind of resolution at all.

There is also a fair, honest argument to be had over how much unprovable accusations about something that happened in adolescence should matter.

Surely, not as much as the character someone has displayed in the decades since. And in that regard, Kavanaugh’s outburst during his own testimony revealed him as a partisan. That may be more telling about his fitness for the high court than his obvious shading of the truth about his rowdy high school and college years.

The Kavanaugh saga has also exposed the degree to which men — and some of the women who love them — feel threatened by the new environment in which they find themselves.

Trump, whose instinct always seems to be to project his own sense of victimhood into other men accused of sexual misconduct, clearly senses a political opportunity in the backlash.

“That’s something to think about, right? That’s something — think of your son. Think of your husband,” he said, adding that the country has found itself in “a damn sad situation, okay?”

The president is not entirely wrong, though perhaps not for the reason he thinks. While false claims are rare, they do happen occasionally, which is why all accusations should be treated with care.

We must also accept that ambiguities and uncertainties will no doubt arise as the country moves toward an overdue reckoning on sexual assault.

Real progress is happening and no doubt will continue to. But the gains are proving fragile. The past few days have told us how much further there is to go.

Read more:

E.J. Dionne Jr.: Trump’s lying, mocking, despicable verbal mugging of Christine Blasey Ford

Paul Waldman: Why Trump may actually want Kavanaugh to go down in flames

Christine Emba: We are all Christine Ford. Or Brett Kavanaugh.

Greg Sargent: Will Trump and Republicans be able to keep the FBI’s Kavanaugh report secret?

Megan McArdle: #MeToo depends on the credibility of the journalists who report on it