In my usual role of discouraging irrational exuberance (or if you prefer, offering a buzzkill), I issued a warning at New York about the need to cool jets despite the outcome of the September 10 debate:

It’s hard to recall a presidential-candidate debate so intensely anticipated as the September 10 encounter between Kamala Harris and Donald Trump, who are locked in a very close race as early voting commences. Now that it’s over, with Harris by near-universal assent being adjudged the winner, many excited Democrats are expecting this “consequential” debate to produce a tangible, perhaps even decisive, advantage for their candidate (particularly since the win was capped with the long-awaited Taylor Swift endorsement of Harris). They should cool their jets.

For one thing, it will take the more reliable pollsters days or even weeks to go into the field and assess the effect, if any, of this event on a contest that’s not just a face-off between candidates but a battle between two deeply rooted and evenly matched party coalitions. Yes, Harris won the CNN “snap poll” of debate viewers: 63 percent thought she won, and 37 percent said Trump won (the latter number showing the reluctance of Trump fans even the most obvious setback for their hero). That’s nearly as large as the margin (67 percent to 33 percent) by which Trump defeated Biden in the CNN snap poll following the June 27 debate. That debate ultimately drove the sitting president of the United States right out of his own reelection campaign. Shouldn’t Harris’ debate win have similarly dramatic consequences?

In a word: no. It’s hard to remember this now, but the June 27 debate did not have any sort of immediate dramatic effect on the Trump-Biden polls. The day of the debate Trump led Biden by a hair (0.2 percent) in the FiveThirtyEight national polling averages; on July 14 he led by a slightly thicker hair (1.9 percent). The debate chased Biden from the race not because he was losing so badly, but because it exacerbated a well-known and central candidate weakness that would make further losses down the road likely and recovery all but impossible. And this calamity occurred just early enough that there was time for Democrats to take drastic but essential action.

Nothing like this is going to happen to Trump. For one thing, his debate performance against Harris, while intermittently shocking, wasn’t at all out of character; his failure was a matter of degree. For another, to the extent there are Republican fears about Trump’s fitness for office or electability, they were crushed many months ago when the former president routed 11 primary opponents. Everyone still in the GOP has bent the knee to the warrior king, he’s overcome far bigger problems in the past, and it’s too late to do anything about it anyway, even if Republicans had a replacement candidate with Harris’s qualifications.

The debate will likely do two important things for Harris. First, it should revive the enthusiasm and sense of momentum that has characterized her candidacy since its launch. This isn’t just a matter of “vibes” but is instead an impetus for previously tuned-out Democratic-leaning voters to reengage with this election, which could have a big impact on turnout. Second, it will address the concerns of many Kamala-curious swing voters about her suitability to serve as president and reflect mainstream values and policy inclinations. That will remain a work in progress given her inherently tricky but essential strategy of offering unhappy voters a change from the status quo even as she remains a heartbeat from the presidency.

This represents very good news for the Democratic ticket, but Team Harris should manage expectations, much as Barack Obama and others did during the DNC when so many excited supporters wanted to believe the wave of “joy” would sweep away all obstacles. She didn’t get a convention bounce and may not get a debate bounce, which means this could remain a dead-even race in which Donald Trump will retain advantages (probably in the Electoral College, possibly in popular support that is stronger than the polls can capture) no matter how foolish or deranged he looked on the stage in Philadelphia.