Donald Trump’s rhetorical blitzkrieg against Fox News Channel star Megyn Kelly is one of the most-talked-about subplots of the 2016 presidential campaign. But there is a basic question that hasn’t been sufficiently answered: why her?

Charlie Rose tried to find out when he sat down with Kelly for an interview that will air this weekend on “CBS Sunday Morning,” according to an excerpt the network broadcast on Friday. The surface-level answer is obvious: Kelly asked a question Trump didn’t like when she moderated the first Republican presidential debate in August. The GOP front-runner said the next day on CNN that Kelly had “blood coming out of her wherever” and has continued to deride her since.

But plenty of other journalists have also asked tough — and, in Trump's mind, unfair — questions. None have been targeted with the same frequency and ferocity.

Kelly addressed her unique treatment during her conversation with Rose.

ROSE: Some think about this, and they look at it, and they say, "Why her?"
KELLY: I think it's very clear to him that he cannot control the editorial on my show, or from me, in a debate or other setting.
ROSE: Just that? That's all it is?
KELLY: I wouldn't want to speculate beyond that.

I can't blame Kelly for not wanting to walk too far down this path, but I'm with Rose — this feels like an incomplete answer. So let's try to fill it in.

Kelly suggested that Trump is bothered by his inability to manipulate her. That's probably true. But, again, Kelly is not alone in this regard. We just watched Anderson Cooper refuse to give an inch during a town hall session with Trump on Tuesday (he told the billionaire to his face that he was acting like a 5-year-old, for heaven's sake), and there was no follow-up Twitter rant about that "overrated," silver-haired "bimbo" on CNN. Sad!

There's more going on here.

For one thing, Kelly hosts the second-highest-rated program in cable news. To paraphrase Trump's long-lost media brother, Ron Burgundy, she's kind of a big deal — on the news channel of choice for conservatives, no less. Turning Kelly into a Trump sympathizer would be a huge win, so it must drive him crazy that he can't do it.

The No. 1 show, of course, belongs to Bill O'Reilly, with whom Trump has (mostly) enjoyed a much friendlier rapport. Even when he vowed to boycott Fox News in the fall — and even when he actually did boycott a Fox debate in January (because of Kelly) — Trump continued to appear on "The O'Reilly Factor." Though he professes to hate the media, the real estate magnate clearly values a show that can give him a large audience.

It seems to me that Trump's fury is directly proportional to how important a host is.

We also can't ignore the possibility (likelihood) that Trump's anger toward Kelly burns all the hotter because he sees her as a woman who — try as he might — he just can't charm. A profile of Kelly in the February issue of Vanity Fair imagined the candidate's frustration: "After all, in his mind, what beautiful woman didn’t want to go to bed with him, right?"

Trump's habit of trying to flatter his way into the good graces of female journalists is well-documented. He tried it last week on his visit with The Washington Post editorial board, when he called Karen Attiah "beautiful." He had used the same line three days earlier on People magazine senior editor Charlotte Triggs, whom he also invited, on a whim, to join him aboard his private jet for a flight to his next rally in Arizona. (Triggs wrote that "campaign aides quickly quash[ed] that," citing Secret Service protocol on background checks.)

Kelly herself has said that Trump turned nasty only after his attempts to "woo" her, as she put it, failed. From the Vanity Fair piece:

In the past, she says, “he would send me press clippings about me that he would just sign ‘Donald Trump.’ And he called from time to time to compliment a segment. I didn’t know why he was doing that. And then when he announced that he was running for president, it became more clear. But I can’t be wooed. I was never going to love him, and I was never going to hate him.”

Put it all together, and it's actually pretty clear why Trump picked Kelly as his media nemesis. It's not just because of one tough question at a debate or because "he cannot control the editorial" on her show. It's also because Kelly is an unattainable female quarry who bruised his ego and just so happens to anchor one of the most-watched hours in cable news — with an audience full of Republican voters Trump desperately wants to reach.

That's a recipe for plenty of resentment.