MILWAUKEE, Wis. — Half the country votes today, including California, New York, and Illinois. So what was Senator Obama doing in Minnesota the weekend right before Super Tuesday?

Packing people into an arena like a rock band for a moment of group identity — 20,000 recruits to the Obama Nation filled the Target Center to cheer the Illinois senator when he showed up in Minneapolis on Saturday. This was a day after Mr. Obama drew 14,000 to an arena in Boise — about thrice as many as those who attended the last Idaho Democratic caucuses. And he got another 20,000 on Sunday in Wilmington, Del. Why? Together, these three states have as many delegates as New Jersey. Why spend the last weekend in small places?

In part because they’re in play. The last poll in Minnesota showed Senator Clinton with scarcely a lead over Mr. Obama. In Illinois, by contrast, Mr. Obama already had a 2-1 lead over Mrs. Clinton.

Moreover, say observers, Mr. Obama was fiddling around in Minnesota to quash any more Clinton-camp lip about his ability to win the hearts of white heartland-America voters. Which he seemed to do, at least the ones who showed up at Target Center. He told a story about finding Senator Wellstone’s name carved into his desk by the late Minnesota Democratic saint. The crowd went mad.

But his speech was mainly his typical national speech, with a lot of talk about hope and togetherness. It had a snitty side. This doesn’t seem to get a lot of attention, but watch the tapes: To the extent that Mr. Obama brings up actual issues, it is to express dissatisfaction. “Our nation is at war, our planet is in peril, the dream that so many generations fought for feels like it’s slowly slipping away,” he told the Minnesotans. And they identified.

Tsunami Tuesday is close to being a national primary. This is not merely so in its 22-state scope but also in what Mr. Obama is making of it: He’s appealing to voters specifically on the nation’s identity and their dissatisfaction with it. It’s not a question of whether the war is good or bad policy, but whether America should be the kind of nation that fights wars.

Take Danielle Arlowe, an Obama supporter from Edina, an upper-crust inner-ring suburb of Minneapolis. Talking to a newspaper reporter, her take on national security was, “I think we’re in a place right now where a lot of the world hates us.” She doesn’t want to be that kind of country and believes Mr. Obama possesses healing properties.

Nor is it just the nation’s identity but that of its inhabitants. Feelings abound among Mr. Obama’s backers: “He is both the Kennedys and Martin Luther King all rolled into one,” one woman told a reporter in Boise. In Minneapolis, another woman compared Mr. Obama’s rally with the way her mother-in-law once saw JFK: “This is our moment in our life that we’ll talk to our kids about,” she said.

That is identity politics — though not as it’s sometimes explained, such as Mr. Obama asking for a vote because of who he is. Rather, it’s a matter of who you will be because you voted for him. He is not doing what Mrs. Clinton is doing, identifying specific Democrat-aligned interest groups and promising specifics.

Instead, he’s seeking people who will support him as self-definition: They vote Obama and are, thus, the sort of people who hope audaciously and who would have supported JFK and who prefer that the world love us. This fits exactly with his pop-star appeal — like buying a tour t-shirt to show the world you’re the sort of person who appreciates the band. Your Obama button isn’t exhortation so much as a boast of superior taste.

Contrast this with the grown-up appeal of Mr. Obama’s chief rivals, talking issues and experience. Mrs. Clinton detained her Minneapolis crowd of 4,000 past the Super Bowl kickoff Sunday to talk about her policy prescriptions.

She showed up later at a St. Paul restaurant to watch the game and didn’t reach her chair until halftime, mainly because she worked her way along the bar, doing politics despite all the TVs everyone else was watching.

This isn’t necessarily generational. I suspect it has more to do with emotional maturity than with actual age. Check the scene of another rally, the much smaller one in Minneapolis on Saturday for Mitt Romney. You want a youth movement? This was a baby boom, with people who reproduce hoisting toddlers on their shoulders. “Marriage first,” Mr. Romney said, getting a big cheer for as adult a sentiment as you’ll find.

Mr. Romney’s probably going to get beat by Senator McCain, whose charm apparently includes his rebel status. Yet the Chicago Tribune’s final poll found conservatives moving toward him because, his offenses aside, they seemed to think he could win the presidency, a triumph of sense over sensibility.

Whether being grown up wins at this moment isn’t clear. You’re up against not only Barack Obama but Oprah and Caroline Kennedy, too, stumping for him in California. You’re up against a nation of victims and those who empathize with them, of retirement-age rock bands, of 35-year-old men who prefer video games to settling down.

It may be a bad year for both the Daddy Party and the Mommy Party, and a good one for the party of people who want to be 22 and trying on new personalities, at least if those arenas full of Obama fans mean anything.

Mr. McIlheran is a columnist for the Milwaukee Journal Sentinel.