When Barack Obama achieved his historic victory on Tuesday night, the battle was joined between two Americas. Not John Edwards's two Americas, divided between rich and poor. Not the Americas split by race, gender, party or ideology. What looms instead is an epic showdown between two wildly different visions of the country, from the ground up.

On one side stands Mr. Obama's resolutely cheerful embrace of the future. His vision is inseparable from his identity, both as a rookie with a slim Washington resume; and as a black American whose triumph was regarded as improbable by voters of all races only months ago. On the other is John McCain's promise of a wise warrior's vigilant conservation of the past. His vision, too, is inseparable from his identity - as a government lifer who has spent his entire career in service, whether in the Navy or Washington.

Given the dividing line separating the two Americas of 2008, a ticket uniting Mr. McCain and Hillary Clinton might actually be a better fit than the Obama-Clinton 'dream ticket,' despite their differences on the issues. Never was this more evident than Tuesday night, when Mrs. Clinton and Mr. McCain both completely misread a one-of-a-kind historical moment as they tried to cling to the prerogatives of the 20th century's old guard.

All presidential candidates, Mr. Obama certainly included, are egomaniacs. But Washington's faith in hierarchical status adds a thick layer of pomposity to politicians who linger there too long. Mrs. Clinton referred to herself by the first-person pronoun 64 times in her speech, and Mr. McCain did so 60 times in his. Mr. Obama settled for 30.

Remarkably, neither Mrs. Clinton nor Mr. McCain had the grace to offer a salute to Mr. Obama's epochal political breakthrough, which reverberated so powerfully across the country and throughout the world. By being so small and ungenerous, they made him look taller. Their inability to pivot even briefly from partisan self-interest could not be a more telling symptom of the dysfunctional Washington culture Mr. Obama aspires to mend.

Yet even as the two establishment candidates huffed and puffed to assert their authority, they seemed terrified by Mr. Obama's insurgency, as if it were the plague in Edgar Allan Poe's 'Masque of the Red Death.' Mrs. Clinton held her nonconcession speech in a Manhattan bunker, banishing cellphone reception and television monitors carrying the news of Mr. Obama's clinching of the nomination. Mr. McCain, laboring under the misapprehension that he was wittily skewering his opponent, compulsively invoked the Obama-patented mantra of 'change' 33 times in his speech.

Mr. McCain only reminded voters that he, like Mrs. Clinton, thinks that change is nothing more than a marketing gimmick. He has no idea what it means. 'No matter who wins this election, the direction of this country is going to change dramatically,' he said on Tuesday. He then grimly regurgitated Goldwater and Reagan government-bashing talking points from the 1960s and '70s even as he presumed to accuse Mr. Obama of looking 'to the 1960s and '70s for answers.'

Mr. Obama is a liberal, but it's not your boomer parents' liberalism that is at the heart of his appeal. He never rattles off a Clinton laundry list of big federal programs; he supports abortion rights and gay civil rights with a sunny bonhomie that makes the right's cultural scolds look like rabid mastodons. He is not refighting either side of the domestic civil war over Vietnam that exploded in his hometown of Chicago 40 years ago this summer, long before he arrived there.

He has never deviated from his much-quoted formulation in 'The Audacity of Hope,' where he described himself as aloof from 'the psychodrama of the baby boom generation' with its 'old grudges and revenge plots hatched on a handful of college campuses long ago.' His vocabulary is so different from that of Mrs. Clinton and Mr. McCain that they often find it as baffling as a foreign language, even as they try to rip it off.

The selling point of Mr. Obama's vision of change is not doctrinaire liberalism or Bush-bashing but an inclusiveness that he believes can start to relieve Washington's gridlock much as it animated his campaign. Some of that inclusiveness is racial, ethnic and generational, in the casual, what's-the-big-deal manner of post-boomer Americans already swimming in our country's rapidly expanding demographic pool. Some of it is post-partisan: he acknowledges that Republicans, Ronald Reagan included, can have ideas.

Opponents who dismiss this as wussy naivete do so at their own risk. They at once call attention to the expiring shelf life of their own Clinton-Bush-vintage panaceas and lull themselves into underestimating Mr. Obama's political killer instincts.

The Obama forces out-organized the most ruthless machine in Democratic politics because the medium of their campaign mirrored its inclusive message. They empowered adherents in every state rather than depending on a Beltway campaign hierarchy whose mercenary chief strategist kept his day job as chief executive for a corporate P.R. giant. Such viral organization and fund-raising is a seamless fit with bottom-up democracy as it is increasingly practiced in the Facebook-YouTube era, not merely by Americans and not merely by the young.

You could learn a ton about the Clinton campaign's cultural tone-deafness from its stodgy generic Web site. A similar torpor afflicts JohnMcCain.com, which last week gave its graphics a face-lift that unabashedly mimics BarackObama.com and devoted prime home page real estate to hawking 'McCain Golf Gear.' (No joke.) The blogs, video and social networking are static and sparse, the apt reflection of a candidate who repeatedly invokes 'I' as he boasts of his humility.

Mr. Obama's deep-rooted worldliness - in philosophy as well as itinerant background - is his other crucial departure from the McCain template. As more and more Americans feel the pain of spiraling gas prices and lost jobs, they are also coming to recognize, as Mr. Obama does, that the globally reviled American image forged by an endless war in Iraq and its accompanying torture scandals is inflicting economic as well as foreign-policy havoc.

Six out of 10 Americans do want their president to talk to Iran's president, according to the most-recent Gallup poll. Americans are sick of a national identity defined by arrogant saber-rattling abroad and manipulative fear-mongering at home. Mr. Obama closed his speech on Tuesday by telling Americans they 'don't deserve' another election 'that's governed by fear.' Of the three candidates, he was the only one who did not mention 9/11 that night.

Mr. Obama isn't flawless. But it's hard to see him hitching up with Mrs. Clinton, who would contradict his message, unite the right, and pass along her husband's still unpacked post-presidency baggage. A larger trap for Mr. Obama is his cockiness. His own tendency to preen and to coast could be encouraged by recent events rocking the Straight Talk Express: Mr. McCain is so far proving an exceptionally clumsy candidate prone to accentuating everything that's out-of-touch about his American vision.

Mr. McCain's speech in a New Orleans suburb on Tuesday night spawned a cottage industry of ridicule, even among Republicans. The halting delivery, sickly green backdrop and spastic, inappropriate smiles, presumably mandated by some consultant hoping to mask his anger, left the impression that Mr. McCain isn't yet ready for prime-time radio.

But the substance was even worse than the theatrics. Incredibly, Mr. McCain attacked Mr. Obama for being insufficiently bipartisan while speaking to the most conspicuously partisan audience you can assemble in today's America: a small, nearly all-white crowd that seconded his attack lines with boorish choruses of boos. On TV, the audience came across as a country-club membership riled by a change in the Sunday brunch menu.

Equally curious was Mr. McCain's decision to stage this event in Louisiana, a state that is truly safe for the G.O.P. and that he'd last visited less than six weeks earlier. Perhaps he did so because Louisiana's governor, the 36-year-old Indian-American Bobby Jindal, is the only highly placed nonwhite Republican he could find to lend his campaign an ersatz dash of diversity and youth.

Or perhaps he thought that if he once more returned to the scene of President Bush's Katrina crime to (belatedly) slam that federal failure, it would fool voters into forgetting his cheerleading for Mr. Bush's Iraq obsession and economic policies. This time it proved a levee too far. The day after his speech Mr. McCain was caught on the stump misstating and exaggerating his own do-little record after Katrina. Soon the Internet was alight with documentation of what he actually did on the day the hurricane hit land: a let-us-eat-cake photo op with Mr. Bush celebrating his birthday in Arizona.

Anything can happen in politics, and there are five months to go. But Tuesday night's McCain pratfall - three weeks in the planning by his campaign, according to Fox News - should be a clear indication that Mr. Obama must accept Mr. McCain's invitation to weekly debates at once. Tomorrow if possible, and, yes, bring on the green!

Mr. Obama must also heed Mr. McCain's directive that he visit Iraq - as long as he avoids Baghdad markets and hits other foreign capitals on route. When the world gets a firsthand look at the new America Mr. Obama offers as an alternative to Mr. McCain's truculent stay-the-course, the public pandemonium may make J.F.K.'s 'Ich bin ein Berliner' visit to the Berlin Wall look like a warm-up act.