So how do we judge last night's debate?
Before we get to what actually happened, we should start with what history -- from past years and this year-- tells us about how to view it.
First, audience. The number of Americans watching no doubt dwarfed the viewership for any prior debate -- including for the legendary first meeting between John F. Kennedy and Richard Nixon. Given the closeness of this contest, and the widespread doubts about both candidates, last night's affair could be unusually influential in determining the outcome.
Second, these events often turn less on substance than on memorable moments -- the gaffe or zinger -- endlessly replayed on our screens. Who of a certain age can forget Dan Quayle's gaffe in comparing himself to the martyred President Kennedy, followed by Lloyd Benson's zinger: "I knew Jack Kennedy. Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy."
To merely quote these lines does not fully capture this moment of devastation. For those too young to recall it, a quick trip to YouTube will prove worthwhile.
Third, never before have two candidates had such contrasting styles. Hillary Clinton tends to be lawyerly, resolute and well-prepared. Donald Trump customarily relies on insults, outrage and serial mendacity, breaking all rules for normal political decorum. The question was whether the format, and the moderator, would reward substance or bluster.
Fourth, as a result Lester Holt's role was critical. Would he be prepared to call out falsehoods? Would he probe the candidates' grasp of issues, the basis for their prior statements or changes in position, the means by which they make crucial judgments? In short, would he help the audience -- at least the more discerning -- take the contestants' measure as potential presidents?
Fifth, many of the undecideds watching no doubt were low information voters, unequipped to assess the policies debated in terms of specifics, yet wary of both Trump and Clinton. Their response was was bound to be more visceral. The question is who more of them liked better and trusted more, and on what basis.
A last question summarizes all the rest: how well did each candidate do in addressing their weaknesses? Clinton's task was to seem more likable and trustworthy or, at least, to persuade more Americans to trust her as president. Advantaged by a bar so low it was almost subterranean, Trump merely had to make "President Trump" more thinkable, especially to a critical mass of undecided voters unprepared to be critical thinkers.
As to all this, prior first debates -- four in particular -- have much to tell us about the dynamics of picking last night's winner.
The first televised debate proved the centrality of expectations and appearances. As compared to Richard Nixon, the incumbent vice president for eight years, John F. Kennedy was a lesser known senator of scant accomplishment. Their debate, it was widely anticipated, would dramatize this gap. Instead, Kennedy came off as crisp, confident, and deeply informed, Nixon's equal as a prospective president -- a draw which, because it surprised, advantaged Kennedy.
But even more telling was how they looked. Kennedy was tan, rested and attractive, the candidate as movie star. Nixon had just spent time in the hospital recovering from an infection, and was drawn, pallid and sweaty -- without makeup, and cursed with a 5 o'clock shadow, he looked more like a shifty-eyed character actor in a crime movie. Even his suit didn't fit; the patrician Kennedy, as ever, was impeccably tailored.
Even for would-be presidents, optics matter. Those who watched television gave Kennedy the edge; by a small margin, the radio audience favored Nixon. But Kennedy had exceeded expectations -- and looked better doing it. He gained an edge which he never lost.
The presidential debate of 1980 had similar dynamics, but may be even more instructive in assessing Trump's performance. Polls showed a close race between President Jimmy Carter and Ronald Reagan. But in itself that spelled trouble for Carter. He was widely regarded as a failed president -- what gave him the edge were pervasive doubts about Reagan's knowledge and judgment. Which made Reagan the combatant with much more to gain.
What transpired was that rare debate which may well have flipped the outcome. In what was widely viewed as a gaffe, Carter cited his adolescent daughter Amy's advice that nuclear weapons were the most important issue - reinforcing a sense of fecklessness. In contrast Reagan was not only an experienced actor but, as a two-term governor of California, a gifted political performer. He looked confident and at ease, dispatching one of Carter's attacks with a practiced zinger -- "There you go again" -- delivered with an indulgent chuckle
Once again, low expectations had served a candidate's smoother performance -- a surprise to many. For millions watching, Reagan had become thinkable as president. He never looked back.
As in prior years, the first debate of 2000 presented an experience gap. Al Gore was the sitting vice president; many voters questioned George W. Bush's acumen and experience. One wildcard was that a considerable segment of the media, while questioning Bush's substance, harbored an intense dislike for Gore -- as the story line went, he was stuffy, or disingenuous, or unresponsive to their inquiries. As the media has tender feelings, this is never a good thing.
Nonetheless, in the immediate wake of the debate the journalistic consensus was the Gore had won. The next morning I went to visit a friend -- a highly-placed Republican professional -- and voiced the same opinion. The gist of his response was this: you may think that now, but wait until we finish spinning the result.
It turned out that Republican operatives had spliced together a tape of Gore, sighing at Bush's answers with showy exasperation. It was, indeed, a lethal affectation, serving the trope that Gore was a pompous stuffed shirt, and swiftly became all the press could talk about.
Gore's win evanesced in an avalanche of changed perceptions. With help from the media, the GOP had snatched at least a standoff from the jaws of defeat. We all remember what happened in November.
The Bush-Gore debate also underscores the media's role in shaping public perceptions of who won or lost. That is particularly salient in 2016, where the omnipresence of social media increases this influence exponentially, insuring a flood of instantaneous opinion. The question was whether a media consensus would emerge, and how that compared with the first reaction of viewers.
Finally, there is a contradictory example -- the first debate of 2012. To the surprise of many, President Obama turned in a lackadaisical performance. Sharp and well-prepared, Mitt Romney walked away from any number of his prior positions, an acrobatic series of flip-flops for which he was never called to account. The near-uniform consensus was that Romney had seriously dented Obama's lead.
Not so much. Obama recovered nicely in the second and third debates. Perhaps more instructive is that, by 2012, our politics was so polarized that Romney's victory seemed to change few minds. Winning the first debate wound up counting for almost nothing.
So, given these precedents, who won last night?
Hillary Clinton, easily.
It was the kind of night she needed. Though this debate will not transform the poll numbers, historians may conclude that it was critical in preserving her electoral advantage.
That this is so owes much to how both candidates performed.
In terms both of substance and optics, Clinton did well. Her responses were crisp, coherent and well considered. On the economy she spoke directly to middle-class voters, and effectively tied Trump to trickle down GOP economics. She navigated the thicket of race relations clearly and effectively. And, in particular, she addressed foreign policy issues in a measured and knowledgeable way, effectively contrasting her experience with Trump's intemperate bluster.
Perhaps more critical, she looked calm, confident and unruffled throughout. The brand of trust she needs to establish is that America would be safe in the hands of President Hillary Clinton. Her manner last night served that goal. And though Trump interrupted her frequently, she maintained her poise, leavened at times by a hint of amusement.
Clinton also succeeded in bringing out the Trump in Trump, hitting him with barbs and attack lines which pierced his all-too-thin skin. As his responses descended into interruptions and irrelevancies, he looked less like a president than an obnoxious ex-husband.
That was the key. Even more decisively than Clinton won, Trump lost.
He started well enough, attacking Clinton on trade and casting himself as an agent of change who would sweep away the failed policies she supposedly represents. Regrettably for Trump, there were 75 minutes left.
What began as a slow-motion train wreck gained speed as Trump reeled to the end. His answers became increasingly garbled, defensive, and pointlessly self-referential -- as usual, he forgot that the campaign is supposed to be about other people. He made all the same old mistakes; lying about his original position on Iraq; clumsily evading his five-year embrace of birtherism; repeating his dystopian portrayal of black communities. None improved with repetition.
It turns out there is only one version of Donald Trump, and it does not wear well over 90 minutes. He was woefully unprepared, unable even to pretend that he knows more than he does -- which, quite evidently, is very little. It was a telling window on a man too self-absorbed to look any better than he is. And he looked even worse when, after he jibed at Clinton for taking time off to prepare for the debate, she responded that she also believed in preparing to be president.
But then Trump looked pretty bad throughout. He grimaced; twitched, sniffed, gulped water and, toward the end, seemed too weary to make much sense even by his own elastic standards. By then he was an easy mark for Clinton's jabs about his history of sexism, racial discrimination and dubious business practices. The alpha male was at risk of becoming a human piñata.
For Trump, this was a lost opportunity on an epic scale. All he needed was to exceed America's very modest expectations, and more independents and wavering Republicans might have come his way. He succeeded only in speaking to the already converted, at most solidifying a base which is too small for him to win.
For Trump is no JFK, Reagan or George W. Bush, underrated candidates who showed their mettle. Trump proved that he was not underrated at all -- except, perhaps, in his own mind. What too many voters saw was a pretender who proved himself worthy of their wariness and unease.
Perhaps the ripest moment came near the end. Asked by Lester Holt to explain his remark that Clinton did not have the look of a president, he said that she lacked stamina -- an unfortunate remark from man who was beginning to resemble a beached flounder. Clinton's response was perfect -- when Trump has visited 100-plus countries, as she did, he should get back to her. One expects that this remark resonated in the souls of more than a few hard-working women.
As for Holt, on a couple of obvious occasions he challenged Trump's statements. But in general he did something far more damaging -- he let Trump speak. Much of the time Trump had nothing much to say, and he said it badly. The audience, on this night, was well served by Holt's light hand. And so a consensus emerged among the media and in early surveys of viewers: Clinton had done well; Trump had not.
As the Obama-Romney debate suggests, given our polarized politics a win in debate does not presage a dramatic shift in voter sentiment. But Clinton likely stabilized her support, while opening some minds among undecideds, wavering Republicans and potential third-party voters. By doing so, she took one large step closer to becoming president.
For one night's work, it was more than enough.