Hillary Clinton and Donald Trump have very different skill sets. As he demonstrated during the first US presidential debate on Sept. 26, Trump excels at shouting; coming up with nearly incoherent insults; and puffed-up caveman machismo. These traits actually served him pretty well during the Republican presidential primaries. But on Monday, they proved to be no match for the specific (and perhaps specifically female) talents of Democratic nominee Clinton.

True to form, Trump—who famously cannot even handle a joke about the length of his fingers—appeared to get progressively more petulant as he realized he was losing. By the end of the night, with Clinton (and the audience!) openly laughing at him, it seemed the Republican candidate was itching to get personal.

“You want to know the truth, I was going to say something extremely rough to Hillary, to her family,” Trump stammered, “and I said to myself I can’t do it. I just can’t do it. It’s inappropriate, it’s not nice.”

Shortly after the debate, Trump and his cronies revealed what his plans to play “rough” entailed. He had considered bringing up Monica Lewinsky at the debate. Now reports suggest he’s champing at the bit to remind voters of the former White House intern scandal. But should he attempt to bring Lewinsky up at the next debate, the strategy would undoubtedly blow up in his face. And the fact that he’s even considering it reveals just how inadequately prepared he is to go up against the likes of Clinton.

Turning Lewinsky into a focal point would be the easiest possible way to make Clinton a more sympathetic figure.

First, I’ll pause so you can get your eye-rolling and groaning out of the way. For one thing, the “scandal” of Clinton’s affair with former White House intern Lewinsky is very old news, dating all the way back to the era of the Spice Girls. For another, to bring up Lewinsky at the next presidential debate, as Republicans lawmakers have warned Trump against doing, would confirm all of voters’ worst ideas about him as a man who rates women on a scale that ranges from sexual trophies at best to “disgusting animals” at worst. But most importantly, turning Lewinsky into a focal point of the US presidential race would be the easiest possible way to make Clinton a more sympathetic figure.

A brief summary of the Lewinsky saga, for those who need a refresher: in the mid-1990s, Clinton’s husband, then-president Bill Clinton, had an affair with Lewinsky, who was working as a White House intern. When the rumors first surfaced, he denied the affair, both to the public and to his wife. When Hillary Clinton learned her husband really had cheated on her, she was reportedly devastated: “She thinks she was not smart enough, not sensitive enough,” wrote Clinton’s confidante Diane Blair at the time.

Lewinsky, who subsequently had details of her sex life and nasty jokes about her body smeared all over every talk-show monologue and tabloid in the nation, found her life in shambles. By contrast, Hillary—cast against her will in the role of the loyal wife—saw her favorability ratings skyrocket, rising from 42% to 64% in the wake of the revelations.

Lewinsky deserves our retrospective sympathy here. Very few of us could stand to have our sexual choices at age 22 paraded before the national media. Yet sympathy for Lewinsky does not preclude sympathy, let alone political support, for Hillary Clinton, unless we are following one very specific, very sexist formulation—the one in which it’s a wife’s duty to keep her husband’s eyes from straying too far, a mistress’s fault for “tempting” a married man, and the one party not to blame for an affair is the man who made a conscious choice to hurt two women.

This suggests a dangerous miscalculation on Trump’s part. Lewinsky would be shaky grounds for attacking Clinton even if she were running against an opponent like Ted Cruz, who at least maintained the typical Republican pretense of upholding “traditional families” and Christian values (of which adultery, famously, is not one).

But trying to discuss Bill Clinton’s affair is even more difficult for Trump, whose has a record of cheating on his (three) wives, and of bragging about the “pieces of ass” with whom he broke his marriage vows. Trump seemingly can’t stop to think about which counter-attacks he’s inviting. His personal strategy of charging as hard as he can, using as many personal insults as he can, means that he almost has to use Lewinsky as ammo against Clinton, even if that means he’ll lay his own marital past wide open and drive up support for his opponent by doing so.

Trump seemingly hasn’t noticed that by continuing to go after Machado, he’s playing right into Clinton’s characterization of him as a bully.

It’s a weakness he’s shown before. This is, after all, the same Trump who’s spent the past week vehemently maintaining his “right” to mock the weight of Alicia Machado, a former Miss Universe who claims that Trump verbally abused and otherwise humiliated her until she developed an eating disorder. Again, Trump seemingly hasn’t noticed that by continuing to go after Machado, he’s playing right into Clinton’s characterization of him as a bully. If the opportunity to call a woman ugly comes up, he has to take it. To back down would make him less than a man.

And that’s the kind of mindset Clinton is counting on. She’s ready for a debate-as-bullfight: Matador Hillary keeps waving her big red cape (or red suit) in front of the bull, so he’ll put his head down and charge. All the while, she’s planning to stick him as he rushes by. Trump has not faced an opponent like this before. Jeb Bush cowered. Marco Rubio and Cruz tried and failed to match the reality TV star insult-for-insult. But Hillary Clinton understands the power of holding her ground and smilingly, knowingly baiting him, reaping the rewards every time he combusts.

If Trump hadn’t underestimated Clinton, he would have known this. She’s used her calm to make opponents look foolish before. In one debate during her run for New York senator, she coolly laughed and smiled at opponent Rick Lazio until he stomped across the stage and waved his papers in her face. It’s a moment that many people believe helped her win the election.

And last year, when Republicans put Clinton on the stand for a marathon 11-hour Benghazi hearing, she gained a massive boost in the polls simply by looking politely bored throughout (and jauntily brushing her shoulders off).

Clinton knows full well the power her composure has to unnerve people. In the wake of the Lewinsky scandal, she told Blair, she went out with her family because “[it] drives their adversaries totally nut(s), that they don’t bend, do not appear to be suffering.” More pointedly, she told Blair that “most people in this town have no pain threshold.”

But few politicians—or people—have a higher pain threshold than Clinton. We spend so much time talking about whether a woman can be president that we’ve scarcely stopped to think about the benefits of nominating one.

While Trump’s mostly-male Republican opponents crumpled in the face of his bullying, she might be the one person his insults can’t ruffle.

To wit, most women have developed the skill of tolerating personal insults, sexist condescension, and personal humiliation in the workplace, keeping a smile on their faces while they do it. Sexism does not give women the option of lashing out, or even appearing to suffer, every time they’re hurt. And few people have had to grin and bear it as often as Hillary Clinton. As a result, while Trump’s mostly-male Republican opponents crumpled in the face of his bullying, she might be the one person his insults can’t ruffle.

And if he can’t get her ruffled, he may not be able to beat her at all. Trump’s right about one thing: Hillary Clinton is not playing nice. She’s doing something better than nice: Being smart. Trump has the “rough” talk option at the ready. But it’s Clinton, with her practiced cool and willingness to goad Trump into meltdown after meltdown, who may well be the presidential candidate best suited to playing dirty in 2016.