Hillary Clinton broke Donald Trump within the first 20 minutes of Monday night’s presidential debate. I spent the rest of it wondering how big the cracks had to get for America to notice.

Trump started with a calm pace and deliberately measured tone: a studiously presidential style. (Even the orange of his fake tan was toned down by layers of TV makeup.)

It didn’t last. The first couple of times that Clinton referred to Trump as “Donald” instead of “Mr. Trump” — even after he, with a flourish so exaggerated that it was nearly Victorian, called her “Secretary Clinton” — you could see him flinch. By the time she admitted her use of a private email server was a “mistake,” and he leaned into his mic to snicker, “That’s for sure,” I knew he’d taken the bait.

Every time he interrupted her — every one of the dozens of times — he got a little more ruffled. She called him “Donald” until he called her “Hillary” — going after her, petulant and red-faced.

“I also have a much better temperament than she has,” he said, finally, wagging a finger in the air.

He made a cryptic reference to a moment at an appearance for the AFL-CIO: “I don’t know who you were talking to, Secretary Clinton, but you were absolutely out of control! I said, ‘There’s a person with a temperament that’s got a problem!’”

The accusation was so patently ridiculous, so clearly rooted in sexist stereotypes (and Trump’s insistence on parroting back every criticism made of him), that Clinton’s reaction wasn’t anger but relief: a laugh, a shimmy, the catharsis of knowing that something has become so obvious that everyone has to acknowledge it’s true.

I recognized that relief; I’ve felt it many times. And then I caught myself.

Would Americans recognize it even if they hadn’t been attuned to subtle sexism? Had they noticed how often he’d tried to interrupt her — or had they just noticed that she talked through his interjections? What would they think of a woman who successfully baited her opponent into showing his true colors?

I spent much of the debate in that state of uncertainty; any reaction I had was quickly second-guessed and pulled back, as I asked myself, “But is that what everyone else in America sees?” Halfway through the debate, I had no idea who I thought would win — because I had no idea how America would respond to a woman who was willing to take the upper hand.

My uncertainty isn’t because it’s unprecedented for a woman to be onstage answering questions at a presidential debate. It’s because I’m all too used to having to look at myself two ways: not only at what I’m doing, objectively, but at how it’s coming off to others.

It’s a perverse way to watch a presidential debate — holding my own feelings and judgments of a candidate in abeyance as I try to control for the presumed sexism of the American public. It’s an even more perverse way to go through life.

Clinton’s provocation of Trump wasn’t civil. But it was impressive.

She didn’t charge directly at him — and she generally used her own answers to stick to policy, making sure she was offering more details than Trump did, then brought up Trump’s own failings as a response to him. But she was merciless, because she was betting he would lose his temper, and he did.

It wasn’t civil. It wasn’t nice. Arguably, it made for a worse debate — if by “debate” you mean a referendum entirely on the ideas of the two candidates, rather than their personal suitability for the presidency.

But Hillary Clinton has never had the luxury of being judged entirely on her ideas. She’s always had to balance the diametrically opposed stereotypes of “leader” and “woman,” to avoid being too grandmotherly or too much of a ball buster.

Faced with an opponent who often comes off as neither a good leader nor a particularly good person, she had to maintain her self-control — to remember all the lessons she’s gotten from decades of public criticism about smiling but not letting herself be talked over, about being knowledgeable but not boring, seeming human but being tough — while Trump lost his.

It was a tremendously impressive performance: alpha as hell. And I spent most of it wondering what other people would think of it.

Every time Clinton kept talking when Trump or Lester Holt tried to stop her, I frowned. I wondered if she was talking too much and dominating the conversation. When she joked that Donald Trump should find out about her policies by picking up her book, I laughed along with the audience — then worried if America would find her superior and smug.

By the end of the debate, it looked too obvious to ignore. When she finally pulled out the coup de grace she’s used in stump speeches — that Trump’s itchy Twitter finger shouldn’t be on the nuclear button — she didn’t need to tell us about Trump’s lack of impulse control; we’d seen it.

When Trump went after her temperament, she gave that shimmy. When he was asked about a slam on her “look,” then claimed he’d actually attacked her stamina, she glanced at the camera and gave what I can only describe as the universal female expression for “Can you believe this shit?”

And only then, toward the very end of the debate, did she bring up Trump’s treatment of women.

Overt sexism is impolite. Pointing out covert sexism is considered impolite. And it’s often unclear where the line gets drawn.

The reason Clinton’s gambit worked is that she took advantage of the same truth that Carly Fiorina used against Trump during one of the primary debates: Overt misogyny, like insulting women about their looks, is generally considered impolite.

Many of Trump’s bigotries — against Muslims and immigrants, for example — are simply considered a blow against “political correctness.” But mocking women and people with disabilities is typically seen as an unacceptable form of punching down.

Undecided American voters — who, let’s face it, are overwhelmingly white at this point — might side with Trump when he complains that you can’t say mean things about Muslims anymore. But they are less likely to believe he’s taking a stance for truth by calling a woman ugly — and more likely to see it as a flaw in Trump’s temperament that he would say such things.

It’s not that all sexism is considered impolite, mind you — just the stuff too obnoxious to ignore. Everything else is rendered invisible to men, and women are expected to act the same way, to navigate around it nonchalantly as if we don’t have to contort ourselves to squeeze between the elephant and the wall.

Point to invisible sexism, and you’ll be accused of seeing things. Lure sexism out into the open — like Clinton did in tonight’s debate — and you could be accused of acting manipulatively, deliberately provoking bad behavior.

That accusation wouldn’t be unfair. But in a leader — in a potential president — that sort of negotiating gambit seems clever and strategic. In a woman, it seems vindictive and weak. It’s just another way the two are set at diametric opposites.

The result is that it is women ourselves who are supposed to know the line between covert and overt sexism. And inevitably, that means a tremendous amount of second-guessing and doubting our instincts. Can I be sure that was because I’m a woman, or was it something I did wrong? Shoot, did that come off the way I intended it to? I know the other women in the room saw what just happened, but did the men see it too?

That last is how I feel about the first presidential debate. People who have accepted that a competent woman can sometimes come off as cold, that a strong leader can smile or laugh as often as she likes without it undermining her gravitas, that it’s okay for a woman to keep talking when a man wants to cut her off — those people saw a winning strategy from Hillary Clinton on Monday.

Early indications are that those people make up a majority of the electorate. We now get to see if America, too, is confident enough to trust its instincts, or whether it starts to second-guess itself — whether Clinton’s dominance gets recast as bitchiness in the days to come.

That would say very little about Hillary Clinton. It would say a great deal about us.