But, in the course of assuming this new political persona, he ditched one of his most potent themes. It was a theme that coursed through his best speeches, like the one he gave after winning the Iowa caucus, and it prompted genuinely stirring moments. A few minutes into his victory speech, he had just finished a refrain about people "choosing hope over fear ... choosing unity over division" when, out of the crowd, there suddenly arose a chant. It was a chant that, while familiar to hockey fans and Republicans, was not one typically associated with Democrats. Obama's supporters were chanting "USA! USA!"

This patriotism was at the very core of Obama's original appeal--the undercurrent of his "one nation" speech at the 2004 convention and his "only in America" autobiographical narrative. And you can understand why it has produced such raw displays of national pride: At a time when Newsweek publishes covers about American decline and polling shows mass despair about the trajectory of the country, Obama's story captures the best about the dynamism and fluidity of our society. It's a shot of idealism when the conversations about our foreign policy and economy have slipped into a despairing realism.

And it's exactly the theme to which he should now return as he turns his campaign toward a Republican foe. The political calculations behind such a pivot are straightforward. The Republicans have already revealed how they will try to portray Obama. Any attacks that smack of race-baiting have the potential to backfire--which is presumably why John McCain has been so reluctant to criticize Obama for the words of his former pastor, Jeremiah Wright. So Republicans will strike a more xenophobic tone. They won't necessarily argue that Obama is actually from another country--although there will no doubt be some subterranean efforts to do so--but they will try to paint him as a cultural foreigner. That, of course, is what McCain is trying to do when he attacks Obama for his association with the former Weather Underground member Bill Ayers or for his "endorsement" from Hamas, as if it makes Obama a terrorist himself. It's not just sleaze but Obama's own negligence that has allowed his greatest political strength to become a liability.

How can Obama counter these attacks? He doesn't have a record of military service to fall back on (although, as the Frenchman John Kerry learned in 2004, sometimes not even that is enough). He's also demonstrated an admirable refusal to engage in the silly symbolism that passes for patriotism. But he does have a simple message that insulates him from any charge that he--and his values--are foreign. As he famously told the 2004 Democratic convention: "We are one people, all of us pledging allegiance to the stars and stripes, all of us defending the United States of America." The criticism launched against him by Clinton and McCain presumes America is irrevocably divided by race and culture. His campaign's central theme is opposition to that prognosis.

Conservatives, too, once appreciated Obama's message. It's a commonplace now among some liberals that the enthusiasm many conservatives displayed for Obama late last year was nothing but political posturing--an effort to diminish Clinton, who they then assumed would be the Democratic nominee. And there's no doubt that some conservatives were being disingenuous in their early Obamamania. But, at the same time, it's not difficult to see in Obama qualities that conservatives could find appealing. Although some now complain that his post-partisan rhetoric has not been matched by a post-partisan voting record, Obama has taken some notable departures from Democratic orthodoxy. On education, for instance, as Josh Patashnik outlined in these pages ("Reform School," March 26), Obama has supported test-based accountability and performance pay for teachers--two things that are anathema to the teachers' unions and that, for the sake of political expediency, Obama therefore sought to downplay in the Democratic primaries.

But, more than any policy positions, it's Obama's state of mind and unorthodox nature that has the potential to appeal to conservatives. As Douglas Kmiec, a conservative legal scholar who's an "Obamacan," wrote in endorsing the Illinois senator, "Obama and I may disagree on aspects of ... important fundamentals [such as abortion and traditional marriage], but I am convinced, based upon his public pronouncements and his personal writing, that on each of these questions he is not closed to understanding opposing points of view and, as best as it is humanly possible, he will respect and accommodate them."

It's his ability to respect and accommodate that Obama should be able to use to great effect against McCain this November. Although McCain himself was once considered an unorthodox politician, he's largely abandoned his heterodox streak. Indeed, the facts are on Obama's side when he argues that a McCain presidency will be, in essence, a third term for the policies of George W. Bush--from Iraq to health care to, perhaps most importantly, the economy. The last issue is Obama's most obvious opening. It's not just the fact that we're headed into a recession and McCain has admitted to having a limited knowledge of economics; it's that he has shifted his position on taxation in wildly divergent directions in a relatively concentrated period of time.

This provides ample ground for attack and contrast. And Obama's opposition to the gas-tax holiday was a return to the unconventional Obama. The controversy over the gas tax shows that the press (and even the public) will reward him for standing on principle in the face of potential political damage. But it was merely a first step. And, now that Obama has apparently dispatched with Hillary Clinton, it's time for him to go back to being the candidate he was when he started his campaign--a candidate of national unity and reconciliation--because that's the candidate who can win a general election.