Joy.

That’s the very first thing Minnesota governor Tim Walz talked about when Kamala Harris introduced him last week as her VP pick. He turned and bowed to Harris, and then said, “Thanks for bringing back the joy.”

Don’t underestimate the power of joy. Of optimism. Of thinking about a bright future instead of being mired in the past or bad-mouthing the present. I think joy, in many ways, is the main ingredient in the propellant that is currently powering the Harris-Walz rocket.

There are several reasons for this. First, Americans—since the founding of the republic—have always been believers and dreamers. That’s why among some of the more recent US presidents, an upbeat slogan, a forward-thinking message, has sometimes provided the margin of victory. I think of John F. Kennedy’s campaign song. I think of the theme of Ronald Reagan’s 1984 commercials. I think of the tagline for Bill Clinton’s origin story. Clinton’s campaign song? Fleetwood Mac’s “Don’t Stop (Thinking About Tomorrow).”

What Harris and Walz are offering is a kind of forward spin that, while not surefire, is reliably stress-tested.

Second, Kamala and the Coach, unlike Donald Trump and JD Vance, are basically happy people: self-assured people, glass-half-full people, people people. It’s no wonder that one of the first things Trump and his surrogates did when Harris was elevated to the top slot was to attack her…laugh. Her “cackle,” as Trump describes it.

As I’ve noted before in this space, I personally find it one of Harris’s most compelling attributes. And it is just plain weird—Grinchian, even—to attack someone because of their laughter, their upbeat take on life’s absurdities, their joy. You know what is truly weird? Trump hardly ever laughs. I’ve never heard him. I mean, maybe when he’s attacking people. But please roll the tape—and listen to pick out a moment he has ever laughed out of sheer joy. People the world over know him instead for his go-to scowl—his Scrooge-like, grump-frump-Trumpian default frown, which the Donald dons like the mask of a bully in a B movie. Exhibit A: that oh-so-serious mugshot. (One can only imagine the late comedian Kevin Meaney’s voiceover: “Get that puss off your face!”)

And his sidekick, Vance, can’t seem to summon much joy either. Last week, when asked by a reporter what makes him happy, he called the question bogus, then gave a litany describing what makes him angry. This ticket just can’t do the positive. To riff on the old Harold Arlen and Johnny Mercer song: They “ac-cen-tu-ate the negative.”

And now Trump not only has to contend with “laughing Kamala” (as he has occasionally dubbed her), but BDE (Big Dad Energy) Walz, the kind of big-hearted guy who named his daughter Hope. Walz was also a football coach. Meaning: He certainly knows how to do the grin and shiv. As John Heilemann (my colleague from Showtime’s The Circus) recently observed about him in Puck: “His vernacular, that kind of Main Street America, and the way he deploys it… just like [fellow Minnesotan] Hubert Humphrey, the happy warrior, he’s smiling while he takes the truncheon out and applies it to your cranium, and the next thing, you’re out. That’s a real skill.”

The joy squad has rattled not only Team Trump but right-wing pundits as well. Even Fox News attack dog Jesse Watters, who has also been known to criticize Harris’s laugh, has voiced frustration about his own mother’s newfound infatuation with the vice president, insisting his mother is “a Kamala fanatic. Keeps talking about joy.”

Third, warmth breeds warmth. It’s called positive reinforcement. Projecting an air of positivity tends to make others (in this case: potential voters) feel positive themselves. And one can feel this energy in the big-time crowds, the spontaneous chants, and the sheer giddiness that has returned to the hustings.

Fourth, the nation has had fear fatigue for so long that the Dems’ campaign has brought waves of relief, hope, promise, and rejuvenated political engagement.

Eight years of MAGA gloom—with a global pandemic in the midst of it—had enveloped the country in a dark cloak. In 2016, Trump won the presidency by mining a deep vein of discontent among the electorate. He constantly spoke of grievance. He spread fear. He helped usher in a national mood of loathing: loathing of a so-called deep state, loathing of the establishment, and loathing of the Other. And he did it by fanning long-simmering resentments among his base—resentments that, at their roots, were often the result of legitimate concerns. Yet, at times, those resentments sprang from a kind of paranoid self-loathing embedded in the belief that the American Dream was somehow unavailable to a huge swath of American voters. From his inaugural address (“This American carnage stops right here”) to his January 6, 2021 call for insurrection (“Stop the steal!”) to four years of social media ranting at Joe Biden and the American judicial process on social media (“The legal system in our country has been corrupted & politicized at a level never seen before”), Trump figuratively polluted the American political atmosphere. When Biden initially handed the reins to Harris and voters responded so enthusiastically, they were evidently starving for a break from the drumbeat, seeking a more optimistic message, even if many may not have realized it at the time. They were primed for the positive.

The phrase “Make America Great Again” has always been about going backward. And in 2016, Trump deftly picked the electoral lock because we were at an anomalous hinge point in history when a slim majority of Americans were so afraid of what the future represented (technology, climate change, the global economy, shifts in migration), that they voted to get into a time machine. But this 248-year American experiment in representative democracy, for the most part, has been about progress, about embracing the future. And we may, in fact, be rerouting ourselves to that tried-and-true path of progress as we see raucous crowds roar in call-and-response cadence, when Harris declares at her rallies: “We’re not going back.”

While there will be battles royale during the next three months over ideology, policy, and personal biographies, I believe this election will fundamentally boil down to a contest between the future and the past, between joy and anger. Indeed, many experts are seeing a surge in young people joining the voter rolls and becoming engaged, offering their opinions, loud and clear. They will certainly play a decisive role in the outcome. The question in this race, at the end of day, will be whether people at the ballot box are inclined to happily embrace tomorrow or bitterly claw back to visions of yesterday.

Which is to say: What’s happening with the Harris-Walz campaign feels fresh and authentic—and different. It feels more like a movement than a moment. And Republican attacks about the ticket being “communist” or “socialist” just feel hackneyed. We’ve seen all of this before. And whatever we feel about politics, most of us are just exhausted by the old and desperate for something new.

As that respected political sage Stephen Stills once observed:

There’s something happening here

But what it is ain’t exactly clear…

Maybe it’s joy. And maybe that simple human feeling can change a nation’s future.