For many months, top Democrats have believed that the single most powerful weapon against Donald Trump is his own words. This was based on scientific testing (polling and focus groups), but also evidence gathered in conversations with voters and family members and fellow Americans in all sorts of casual and formal settings alike.

The basic case Dems have made against Trump has been fairly simple: Someone who is so cruel, so abusive, and so openly, obviously eager to prey on people’s basest instincts, has no business being president — someone who takes such obvious sadistic pleasure in demeaning and belittling others, whether individuals or groups, simply cannot be president. It’s unthinkable.

This is why the video of Trump mocking a disabled reporter has perhaps been featured in more Democratic advertising than anything else. It is why ads showing children watching Trump spew insults and curses and glorifications of violence and thuggery have run in heavy rotation in swing states for months. It’s the basic underlying idea behind that viral Clinton ad showing Trump spraying hot misogyny in all directions as girls who are on the verge of making the already-frightening transition to adulthood stand face-to-face with mirrors, looking puzzled, sheepish, and a touch worried.

In a speech today, Michelle Obama summed up this whole argument as well or better than anyone has so far:

Michelle Obama is a tremendously popular public figure, who is probably better positioned than anyone else in the country to make this particular case. And that’s what makes this a seminal, defining moment.

Trump had his chance to try to prove that this isn’t who he is. We were told for months and months that a “pivot” was coming. We were told again and again that, now, finally, Trump was going to show that the hateful, bigoted, sexist, xenophobic, birther-mongering figure who has screamed from our TV sets for the past year was not the real Trump — it was all an act, and now he’d surprise us all by showing the real Trump to the majority of the country who seemed to be in the process of deciding that he was fundamentally unacceptable.

But it never happened. If Trump has a capacity for basic and sustained public decency, it has yet to make its appearance. And now we really seem to have crossed a point of no return. Michelle Obama marked it down. No going back.