Note: This column has been updated in light of Tuesday’s election results.

DOWNINGTOWN, Pa. — The result of the 2008 election may come down to how voters decide to define Barack Obama. Is he Adlai Stevenson or John F. Kennedy? Is he a detached former law review editor or a passionate agent of change? Is he an upscale reformer focused on process or a populist who will turn Washington and the country around?

One of the central lessons of the Pennsylvania primary campaign is that Obama’s personality is now far more important than either Hillary Clinton’s or John McCain’s. That’s true not only because voters have a longer history with Clinton and McCain, but also because so much of the energy and novelty of 2008 is the product of Obama’s rapid breakthrough.

As a result, almost all of the turns in this contest have been driven by how Obama presented himself and how voters perceived him.

Obama was steadily cutting Clinton’s lead in Pennsylvania until the wide attention given to his comments about “bitter” and economically frustrated voters who “cling” to religion and guns. His advance was stopped, allowing Clinton to win a solid victory on Tuesday that will keep the campaign going.

When Obama is in control of his own image, his moments of detachment and irony are celebrated as bearing remarkable similarities to those of the cool, shrewd and confident JFK, who won in 1960. When doubts about Obama creep in, those same characteristics are disparaged for resembling the diffidence and distance of Stevenson, who lost in 1952 and 1956.

At its most exciting moments, Obama’s campaign has been compared to the great crusades for change in our country’s history. His appeal to African-Americans and the young of all races has led enthusiasts to see his effort as the reincarnation of Robert F. Kennedy’s brief, glorious and tragic 1968 run for the presidency.

But when Obama falls into the long pauses he is sometimes given to the visible impatience he exhibits toward the less-elevating aspects of politics, he seems far more the law review editor, the classic good-government guy whose reach to hard-pressed, white working-class voters is limited. Such voters were key to Clinton’s Pennsylvania victory.

Occasionally, these very different Obamas show up at the same time. More precisely, the same words can be heard as ratifying either version of his story, depending on the assumptions a listener brings to them.

At a campaign rally here Saturday during a whistle-stop tour across Southeastern Pennsylvania, Obama laced into Clinton for “the say-anything, do-anything style of politics that has become the habit in Washington.”

Without mentioning last week’s ABC News debate, much assailed for becoming a staging point for one attack on Obama after another, the candidate was clearly courting a backlash against “a politics that’s all about tearing each other down.” And he continued to scold Clinton for accepting contributions from lobbyists.

Seen by Obama’s critics, this is a discourse about process rather than problems. It seems to highlight procedural reform, not the delivery of concrete benefits to people who need them. But his enthusiasts see his words as those of the only candidate who can break with Washington’s partisan polarization and the nation’s festering divisions, particularly those around race and class.

In separate interviews, the Democratic candidates’ two leading Pennsylvania supporters cast the choice almost exactly this way. Gov. Ed Rendell, Clinton’s staunch advocate, explicitly compared Obama to Stevenson and then contrasted the diffidence implicit in the metaphor to Clinton’s own image.

“Her campaign has been spotty at best,” Rendell said, “but the one thing they’ve done a good job at, and in many ways Hillary deserves credit for this, is portraying her as a fighter.”

Clinton embraced this image in her victory speech on Tuesday night. “I’m in this race to fight for you,” she declared, “to fight for everyone who’s ever been counted out.”

Sen. Bob Casey, who has described Obama as “the one national leader who can bring our country together and begin to change the future,” told me he was astonished at the energy Obama has created in such a short time and the “ever-flowing stream” of loyalists who showed up at his events, even in the smallest Pennsylvania towns.

Obama still inspires such enthusiasm, but in Pennsylvania, as in Texas and Ohio last month, it was not enough to close the deal. The Obama experienced by such devotees is not the candidate that all voters see.

E.J. Dionne’s e-mail address is postchat(at)

© 2008, Washington Post Writers Group

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