Fox News Channel moderator Megyn Kelly was at center stage for Thursday's Republican presidential debate in Des Moines. (Reuters/Carlos Barria)

There was no avoiding it, and Fox News Channel didn't really try: Megyn Kelly was the star of the show at Thursday's Republican presidential debate in Des Moines.

Kelly, of course, is a big reason that GOP front-runner Donald Trump refused to participate. Ever since their run-in at the first primary debate in August, Trump has maintained that Kelly is a "lightweight" who doesn't ask fair questions. (Never mind that he previously said she's a great moderator.) Unreasonable as Trump's critique might be, all eyes were on Kelly and her questions in Des Moines.

Seated at center stage, between co-moderators Chris Wallace and Bret Baier, Kelly posed the first question of the night, to Sen. Ted Cruz of Texas, and went right after what she referred to as "the elephant not in the room."

KELLY: Donald Trump has chosen not to attend this evening's presidential debate. What message do you think that sends to the voters of Iowa?

Donald Trump didn't attend the Fox News GOP debate on Jan. 28, but that didn't stop nearly everyone from talking about him. (Jenny Starrs/The Washington Post)

Kelly was obviously teeing up a softball for Cruz, who had slammed Trump for his decision to withdraw from the debate. It felt a little like getting someone else to do her dirty work.

But after that, the "Kelly File" host was strong throughout the rest of the evening, pushing back with a cool composure at important moments. At one point, New Jersey Gov. Chris Christie embellished what neighbors of the San Bernardino shooters claim to have known before the December attack that killed 14. Kelly would have none of it.

CHRISTIE: They knew they were talking about the issues of attacking people, Megyn. They knew that.

(Crosstalk)

KELLY: That's not true. The neighbors said they saw men going in and out of the garage. They saw packages being delivered. They saw Muslims, and they did not think that was enough to call the cops.

To fact-check Christie on the spot here required a total command of the details and a level of assertiveness that we haven't always seen from moderators in this election cycle -- or any other. It was a great moment for Kelly.

But one question, in particular, perfectly captured what makes Kelly so fearsome.

KELLY: Senator Cruz, when Senator Rubio proposed that bill creating a path to citizenship, you proposed an amendment. It would have allowed for legalization but not citizenship. Yes, it would. Pressed last month on why you supported legalization, you claimed that you didn't. Right? Like you just did. Saw that.

(Audience laughter)

You argued that this was just a poison pill amendment — basically it's something designed to kill the bill and not actually get it through. But that is not, however, how it sounded at the time. Watch.

Kelly then played old video of Cruz explaining the purpose of an amendment he filed on a 2013 immigration bill.

Neither cameras nor microphones picked up whatever Cruz said or did while Kelly was asking her question -- and drew her "saw that" comment -- but we can infer that he objected to the claim that his amendment "would have allowed for legalization." Kelly managed to insist that she was right — and she was — but do so with a humorous quip that made the audience laugh. In an instant, the crowd was on her side. Even Cruz, who loves to complain about the media, knew better than to lash out at Kelly like Trump has. He defended his record as strongly as he could, but he didn't criticize her or her question.

This is the Kelly magic: she can be confrontational and charming all at once. It's easy to argue with a journalist no one likes, but it's much tougher to pick a fight with one who so easily wins over the viewers you hope to turn into your voters.

Trump has no problem bashing Kelly on social media, but he wasn't willing to step back onstage with her, where he would have had to contend with the dynamics of a live audience. One question to Ted Cruz showed exactly why.

READ MORE:

The long, strange history of the Trump and Kelly feud

Campaign or 'The Godfather'? Fox says Trump camp threatened Kelly.

The real reason Trump skipped the Fox debate

Trump once said debate dodgers lack courage

Winners and losers from the debate

The debate transcript, annotated: Who said what and what it meant