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When Donald Trump and Joe Biden take the debate stage in Cleveland tonight, many in the audience will want the moderator, Chris Wallace, to fact-check the candidates aggressively. Political partisans are like basketball fans: They want to see fouls called on the opponent, not on the home team. Yet Wallace and the moderators of subsequent debates will have to find balance, just as NBA referees do. Letting players get away with the most flagrant violations—say, treating dribbling as optional as they get their steps in on the way to the hoop—would ruin the game, but refs don’t call every foul, because doing so would essentially stop play.

Debates at their best offer glimpses into each candidate’s temperament, character, and style of leadership. Whether a candidate tells a lot of whoppers during a debate certainly matters. Hence the minor uproar on Twitter when Frank Fahrenkopf, a co-chair of the presidential-debates commission, said Sunday that the group doesn’t expect its moderators to be fact-checkers. Some debate viewers will feel disappointed, even personally wronged, when false statements by the other side go unchallenged. But to reduce the moderator’s job to real-time fact-checking is to fundamentally misunderstand what debates are for.

For the record, I am a fan of getting the facts straight during a debate. I was booed for doing so while moderating a Republican-primary debate in 2016, during a discussion about the standard for when to nominate Supreme Court justices in an election year. But I also have the perhaps naive hope that debates can illuminate dynamics of the presidential race that voters do not already know—and reveal things that they cannot learn without seeing the candidates go head-to-head.

Fixating on a candidate’s misstatements isn’t synonymous with telling voters what they most need to know. A story largely lost in the news cycle earlier this month shows why. In a September 15 interview on Fox & Friends, Trump disclosed that he had wanted to assassinate the Syrian leader Bashar al-Assad. “I would have rather taken him out. I had him all set. Mattis didn’t want to do it,” Trump said, referring to then–Defense Secretary Jim Mattis. “Mattis was against most of that stuff.”

Because Trump denied last year that he’d considered any such thing, many stories about his comments focused on whether he was speaking accurately. By The Washington Post’s count, Trump has made more than 20,000 false or misleading statements since taking office. Here was one more. Yet Trump’s statement about potentially assassinating Assad raised many other questions: Why did the president want to do that? What distinguished Assad from other authoritarians, such as North Korea’s Kim Jong Un, whom Trump seeks to work with? How did Trump think Assad’s allies Russia and Iran might react? After killing Assad, what obligation might the U.S. have had to send its own forces to stabilize Syria? Why was it wrong for Mattis to stop Trump—or was it wrong? If the president seriously considered assassinating Assad, voters deserve more information about his thinking. The list of questions only grows if the president was just blue-skying on morning television the idea of killing a foreign leader. Before the Gulf War, Defense Secretary Dick Cheney sacked a general for making similar comments about Saddam Hussein.

The Assad story is a reminder of the stakes in presidential debates. Americans, in any presidential election, are giving power to someone to kill others on the nation’s behalf. Voters are also entrusting their own well-being to the president. This year’s debates occur against an accumulation of crises, including a deadly pandemic, protests over racial injustice, and a sudden recession.

Presidents sometimes must keep secrets. The office was created with that in mind. Dwight Eisenhower believed he was protecting American interests when he falsely told the Soviets that the U.S. was not flying planes overhead to spy on them. (He was busted when the U.S.S.R. presented the pilot Francis Gary Powers from a downed spy plane.) You could make the case that lying about plotting to kill Assad—or about not plotting to do so—is also in America’s national-security interest.

Not all lies are equal, though. Trump knew that COVID-19 was “more deadly than even your strenuous flu,” as he told the journalist Bob Woodward. But in public, he repeatedly likened it to the flu—giving the impression that the coronavirus was less harmful than it was. I’d like to hear from the candidates when they think a president is justified in lying—and when lying is impermissible. How candidates manage this answer would tell us something about how each might manage some of the job’s trickiest challenges.

What all the moderators know is that simply asking a question may not produce a worthy answer. In many cases, all it yields is a response, which is something very different. This is where moderators could step in to seek a more substantive answer—which might sound like fact-checking, but is not. If moderators are trusted to come up with revealing questions, they need the leeway to press the candidates on voters’ behalf to get answers.

If a candidate gives evasive or dubious answers when asked about vital issues, debate viewers can and do pick up on the pattern. A candidate who takes a question about topic A and answers one about topic B, because that issue is better for them politically, is trying to trick voters. A candidate who answers a pointed question with a spray of words is telling the public that his or her decision making lacks a firm foundation. Voters might expect such a candidate to behave similarly in office, offering haphazardly improvised responses to problems that can be solved only through preparation and sustained focus. Debate answers of this sort can illuminate which candidate’s White House staff will devote its time and attention to forward progress, and which candidate’s style of governing consists of repeated cleanups on aisle nine.

Candidates show a lot by what they don’t say and the attributes they don’t demonstrate in their answers. A response that reveals a lack of empathy or self-control is not one a moderator can fact-check, but it reveals blind spots that a presidential candidate will carry to the nation’s highest office.

No one wants to see an event with such a huge audience become a platform for deceit, but in the end, the structure of debates leaves this risk open. When and if a moderator chooses to step in on behalf of the facts, considerable skill will be required, given the running clock. A moderator must have a battery of knowledge sufficient to evaluate the veracity and adequacy of answers on a wide variety of topics, choose whether to do so while continuing to listen to the response (which might include bigger whoppers), decide which fibs and evasions to highlight, keep track of the time, and make sure that any fact-check frames the nature of the error completely and in context, applying the same standard to both candidates—all the while determining whether intervening at a given moment is of sufficient value relative to the larger goals of the night.

Some candidates, including Trump, treat fact-checking not as something to worry about but as a second round of publicity. They’re willing to pay what they believe is the small penalty of being called out for a factual error, for the larger benefit of having the post-debate news coverage spread misleading bits of information. Trump’s past conduct suggests that he will be poised to turn any fact-checking moderator into a foil, crying foul to undermine the process. Biden has indicated that he will try to fact-check the incumbent during debates. That could prove effective—or it could encourage his opponent to keep him terribly busy. Challengers who focus too much on correcting the record may not leave enough time to make a positive case for themselves. If they make a habit of fact-checking and then don’t complete the task, they leave the suggestion that the unanswered claims were true.

Viewers don’t have to rely on moderators or candidates to do all the fact-checking. In the end, the burden is on those watching. They can evaluate the post-debate coverage, which offers context about the tonnage of falsehoods and which candidate was responsible for the larger share. Not all deception is alike, and some infractions are worse than others. Rather than expect Wallace or anyone else to establish the truth live, citizens would be wiser to wait and weigh all the evidence before reaching what should still be a grave conclusion: that, with the whole world watching, a candidate chose not to tell the truth.

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