"I'm not going to call her honey," Trump said in an interview last week. But he added of Fiorina: "Look, she's only got 3 percent in the polls, so in order to get recognition, I think she'll start hitting me. So I think she's fair game."
Trump said he was preparing to criticize the record -- and not the appearance -- of Fiorina, who was fired as the chief executive of Hewlett-Packard and, like Trump, has never held elected office.
"I want to talk about her corporate history, her failures at Hewlett-Packard," Trump said. "And that will be damaging enough to her."
The usual rules of decorum have so far not applied to Trump, whose standing in the polls has only increased after incendiary comments about women, immigrants and Sen. John McCain's war record. But while his derision of two opponents -- Jeb Bush ("low energy") and Gov. Scott Walker of Wisconsin ("failed governor") -- has coincided with their decline in the polls, Fiorina has gained ground as Trump has showered insults on her.
Fiorina responded to Trump's comments in Rolling Stone magazine ("Can you imagine that, the face of our next president?") by telling Fox News, "Maybe, just maybe, I am just getting under his skin a little bit because I am climbing in the polls."
Trump eventually said that he was referring to Fiorina's "persona" when he made the remarks about her face.
Fiorina, 61, has said that, as a successful woman, "you're either a bimbo or you're the other b-word," and that "there is no glass ceiling." She is often defensive when asked about whether her gender has helped her get ahead, and yet she has seized on her position as the only woman in the 16-person Republican field.
Fiorina started her long-shot candidacy by taking direct aim at Clinton, but she now appears poised to be the best candidate to bring out the side of Trump that has drawn accusations of misogyny -- a tactic some Republicans hope Fiorina will embrace on Wednesday.
"Instead of shutting him down, there's a way to pat poor Donald, the chauvinistic pig, on the head," said Rob Stutzman, a Republican strategist in Sacramento, California.
Trump said he would not be chauvinistic.
"I wouldn't do that; I won't do that," he said. "Though, if I did -- well, people would just hit me with political correctness, which, again, people are so tired of."
In the first undercard debate, Fiorina seemed prepared and calm under pressure. Her rivals treated her mostly with respect or deference, but the stakes will be higher on Wednesday. Fiorina and her supporters aggressively lobbied CNN to alter its criteria for picking candidates for the next Republican debate, securing a spot for her on the main stage.
"This is going to be a defining moment in Carly's career," said Boris Feldman, a Silicon Valley lawyer and one of her supporters.
"What's selling tickets to this is the Trump-Carly card," he said. "Trump has a thing about anybody questioning him, but especially a woman."
Feldman and others close to Fiorina expect her to portray Trump as not being a real Republican, and to call out his inconsistent positions on economic and social issues.
Fiorina has a bare-bones campaign staff and has been preparing for the debate by adjusting her standard responses and zingers to fit into the succinct format. She works mostly in a sunny room of her Colonial-style Virginia home with her husband, Frank, and their two Yorkshire terriers, Max and Snickers, nearby, and she communicates with aides on a speaker phone.
Fiorina declined to comment for this article.
Political strategists on both sides advised Fiorina either to ignore any potentially sexist attacks by Trump or to engage him in a way that is different from what the men onstage do.
"If I were her, I would have a little fun with Trump," said former Rep. Patricia Schroeder of Colorado, who sought the Democratic presidential nomination in 1988. She suggested that Fiorina cover her face with her hand and say, "I don't want to upset or distract you, Donald, if my face really bothers you."
Debating female candidates can be perilous even for men who do not have Trump's reputation for insulting women, which includes calling a female lawyer "disgusting" after she took out a breast pump, and joking about oral sex with a female contestant on NBC's "The Celebrity Apprentice."
As Joe Biden, a senator at the time, prepared for his vice-presidential debate against Gov. Sarah Palin of Alaska in 2008, he received some very clear rules from his advisers, according to several people who helped him plan: Don't correct her, don't belittle her, don't mock or diminish her.
"Carly Fiorina is a better debater than Gov. Palin, and she has a great capacity to take on Donald Trump," said former Gov. Jennifer M. Granholm of Michigan, who played Palin in Biden's mock debate sessions.
Trump's plan to attack Fiorina's corporate record could make an effective impression. Voters know little about the layoffs during her rocky tenure at Hewlett-Packard or about her $21 million severance package, something that Sen. Barbara Boxer of California highlighted in their 2010 Senate race. Boxer defeated Fiorina by 10 percentage points.
"They'll understand pretty quickly that she is the face of income inequality and Wall Street greed," Boxer said in an interview. (Fiorina has said the layoffs and her subsequent firing were reflective of the bold leadership she brought to the company.)
Deborah Bowker, a close friend and an aide to Fiorina, said that after years of being surrounded by men in corporate America, Fiorina was unfazed by Trump.
"This isn't the first time she's been confronted by someone making a crazy comment," Bowker said. "She has had comments about her looks, her clothes, whatever."
That is at least one point on which Trump and Fiorina can agree. "I think she's a strong woman," he said in the interview last week. "She can handle any criticism of her, and she can defend herself."