Moderators Anderson Cooper and Martha Raddatz addressed the audeince before the second presidential debate between Donald Trump and Hillary Clinton. (Jim Young/Reuters)

Anderson Cooper, one of the country's most recognizable journalists, doesn't need much of an introduction. But since Cooper has never moderated a general-election debate before, you might not know what to expect when he and ABC's Martha Raddatz run the show Sunday night in the second meeting between Hillary Clinton and Donald Trump.

So here are five things to know about Cooper that might provide some clues.

Donald Trump started accusing Cooper of bias three weeks before the debate

Trump loves to complain about moderators. He did so frequently during the Republican primary, most notably when he boycotted a Fox News debate over the network's unwillingness to replace Megyn Kelly. The Republican presidential nominee refused to commit to the general-election debates until he saw the list of moderators, and even then he claimed (falsely) that "they're all Democrats."

But Trump has been particularly critical of Cooper.

"I don't think Anderson Cooper should be a moderator because Anderson Cooper works for CNN, and over the last couple of days, I've seen how Anderson Cooper behaves," Trump told The Washington Post's Robert Costa last month. "He'll be very biased, very biased. I don't think he should be a moderator. I'll participate, but I don't think he should be a moderator. CNN is the Clinton News Network, and Anderson Cooper, I don't think he can be fair."

Cooper was very tough on Trump at a town hall event in March

It is often hard to trace the root of Trump's media feuds, since minor, seemingly forgettable slights can stick with him. But a decent guess at the origin of his beef with Cooper is a town hall event in March.

Cooper followed up and fact-checked Trump consistently throughout the night. An irritated Trump dropped 18 "excuse mes" on Cooper during the one-hour session, in an effort to retake control of the conversation. At one point, when Trump defended a nasty retweet aimed at Ted Cruz's wife by saying "I didn't start it," Cooper offered a memorable retort: "But, sir, with all due respect, that's the argument of a 5-year-old."

Cooper has hinted at a more hands-off approach on Sunday

Though he was dogged at that town hall event in March, Cooper has indicated that viewers should not expect a repeat performance this weekend in a debate that also will be conducted in the style of a town hall meeting.

"I think there is a value in stepping back," he said on the air last week. "You don't want it to be about you. You want it to be a discussion about the two, and if one is interrupting the other, that tells the audience something, and people can make up their own minds about what exactly that means. I'm not sure it's always good for the moderator to be stepping in and trying to direct and keep everything to time."

Cooper has questioned Clinton about her honesty

Moderating the first debate of the Democratic primary last year, Cooper led off with this pointed question: "Plenty of politicians evolve on issues, but even some Democrats believe you change your positions based on political expediency. You were against same-sex marriage. Now you're for it. You defended President Obama's immigration policies. Now you say they're too harsh. You supported his trade deal dozens of times. You even called it the 'gold standard.' Now, suddenly, last week, you're against it. Will you say anything to get elected?"

With that question, Cooper put his finger on voters' doubts about Clinton's honesty and trustworthiness — a consistent weakness for the Democratic nominee in polls. It would be no surprise to see Cooper return to the theme on Sunday in a setting where the candidates will interact with voters in the audience.

Cooper just signed a long-term extension to remain at CNN

Sorry, everyone who was hoping for "Live with Kelly and Anderson." Cooper last week signed a long-term extension to remain at CNN. The anchor didn't exactly shut down speculation that he might leave his news show to become Kelly Ripa's daytime co-host when asked in April about the possibility on "Watch What Happens Live." But it turns out that Cooper is staying put, which means that he could moderate another debate in a future election.

Cooper will still join Ripa as an occasional fill-in host, according to the Hollywood Reporter. In fact, he will co-host on Wednesday, just a few days after the debate.