Megyn Kelly has stood up for other women offended by Donald Trump. (Photo by Jesse Dittmar for The Washington Post.)

With a single word, Fox News Channel star Megyn Kelly weighed in Thursday on Donald Trump’s latest juvenile antic — this one involving a photo illustration that the Republican presidential front-runner retweeted just before midnight.

The illustration juxtaposed two images: One of Ted Cruz’s wife, Heidi, making a facial expression that she probably wouldn’t pick for a portrait, and the other of Trump’s wife, Melania, Vogue-ing like the former supermodel she is.

Trump’s tasteless retweet continued an attack he started on Tuesday, when he cryptically threatened to “spill the beans” about Heidi Cruz.

And Kelly’s response continued what is becoming a trend in this lowest of low-brow campaigns — generally letting Trump go after her, until the attacks involve other women.

The “Kelly File” host is, of course, Trump’s favorite female target, going back to the first debate of the Republican primary season. As a moderator of that event, Kelly cited Trump’s history of disparaging remarks about women and asked if he possesses a presidential “temperament.” The next day, the billionaire real estate mogul said Kelly had “blood coming out of her wherever,” launching a sub-campaign of hateful commentary about the journalist that continues to this day.

Republican Donald Trump skipped the debate where Fox News anchor Megyn Kelly co-moderated. Here's a look back at the clash that started with an earlier debate in August 2015. (Sarah Parnass/The Washington Post)

Just last Friday, Fox News felt compelled to issue a statement denouncing Trump’s “sick obsession” with one of the network’s top draws.

But Kelly has mostly ignored the insults, perhaps not wanting to give Trump the satisfaction of seeing her rattled and desiring to stay journalistically neutral. In August, for instance, she acknowledged on her show that Trump had "attacked me personally" but said she had "decided not to respond." Earlier this month, she moderated another debate in which Trump participated, and she did not confront him or treat him any differently from the other candidates.

When others are harmed, however, Kelly seems to have a lower tolerance level. After a Breitbart News reporter accused Trump campaign manager Corey Lewandowski of grabbing and yanking her arm at a news conference this month, the reporter, Michelle Fields, gave Kelly her first TV interview. And Kelly was unequivocal about what she saw in the campaign's attempt to deny anything happened and to cast Fields as a serial liar.

"They're basically trying to destroy her," she told viewers.

In February, Kelly condemned the hostile environment at Trump rallies after a man in the crowd cursed at NBC News reporter Katy Tur. She needed two words this time.

In a cover story for the February issue of Vanity Fair, writer Evgenia Peretz described Kelly as "a feminist icon of sorts — the sort who won’t actually call herself a feminist."

What with all the male bullies she’s put in their place, Kelly would be perfectly positioned to become a leader in women’s issues such as equal pay and reproductive rights. But Kelly, whose position on abortion, she says, is known only to her husband and herself, claims these issues actually divide women. “Why can’t there be an acknowledgment that, in some instances, women remove themselves from the workforce for a long time and, when they come back, of course they’re not going to get exactly equal pay?” she asks. “It’s like some of these things are anathema — if you say them, you get booted out of the feminist club. … Gloria Steinem doesn’t get to kick those other women out of the feminist club, or the female-empowerment club, because she says so!” Sensing herself getting uppity, she laughs and does a sassy snap across her face for emphasis.

Kelly might not fit the conventional mold of a feminist crusader, but in this election, she is emerging as a prominent ally for other women targeted by Trump and his supporters. It's probably not a role she wanted to fill. On that August episode of "The Kelly File" where she refused to fire back, she added that her desire was to "get back to the news."

Too often, however, the news is Trump's lack of respect for women. And Kelly isn't letting it slide.

Donald Trump certainly isn't the first person Megyn Kelly has asked tough questions. (Peter Stevenson/The Washington Post)