Watching television footage of George Bush's first inauguration, you can see how nervous he was -- his body tense, his eyes darting back and forth. His suit seemed half a size too big, and he confessed to a television interviewer that he was afraid he might cry when he saw his dad on the podium.

That George Bush is gone. He grew into his job and into himself after Sept. 11, 2001. You can question many of the decisions he has made, and his style of governing, and still recognize that he has emerged as a political leader. This time the suit fits, the voice is firm, the man is fully formed. Yet the story isn't complete.

Bush's second term will take the measure of this president, a man whose character remains at once transparent and opaque. For all his sunny confidence in freedom and his resolute sense of purpose, he stands at the precipice of what increasingly seems likely to be a failure of American foreign policy in Iraq. Nobody can predict the long-run future of Iraq, but over the course of Bush's second term, this story is unlikely to have a happy ending.

Something in Bush resists the tragic sensibility that other presidents conveyed at similar moments. On the eve of his second inauguration, in 1917, Woodrow Wilson -- a rare match for Bush in his idealism about American values -- had a deep foreboding about America's entry into World War I, which he knew by then was all but inevitable. The historian Gary C. Woodward writes that Wilson "doubted that the Constitution could survive a major war."

Lyndon Johnson similarly approached his inauguration in January 1965 vexed by America's deepening involvement in Vietnam -- a war that he suspected would turn out badly but that he still could not escape. Michael Beschloss's collection of Johnson's telephone conversations includes this haunting comment to his defense secretary, Robert McNamara, just over a month after a triumphant inauguration: "I don't think anything is going to be as bad as losing, and I don't see any way of winning."

Even Bush's father had that tragic fatalism about war. A compilation of his personal letters includes this Dec. 31, 1990, note to his children about the Persian Gulf War that was just a few months ahead. "I guess what I want you to know as a father is this: 'Every Human life is precious.' When the question is asked, 'How many lives are you willing to sacrifice?' -- it tears at my heart. The answer of course is none -- none at all."

What gives Bush his strength, and what won him reelection, may be precisely the fact that he isn't the sort of complex, brooding man who is the stuff of tragedy. The direct, what-you-see-is-what-you-get aspect of his character isn't feigned.

The essential Bush is evoked by Joseph Ward, a Yale classmate and fellow member of the "jock" fraternity, Delta Kappa Epsilon. "I remember him as being comfortably one of the group -- not trying to be important, not trying to be special. That was why people liked him." Bush had the same cockiness and stubbornness as now, and people made fun of him for the same reasons -- that he wasn't smart enough, or that he pretended to be a southern good ol' boy, "but none of it seemed to bother him," remembers Ward, who is now wine editor of Conde Nast Traveler.

In his second term, Bush's story will be driven to a deeper level. The amiable optimist will have to deal with the darkest decision a president can face: what to do when a war goes badly. Will he be ground down by no-win choices, as LBJ was? Will he get lucky and somehow escape with limited damage? Will he hunker down for four more years of what his defense secretary rightly called "a long, hard slog"? Whatever he decides, it will define his presidency.

This is Bush's third chance to become a president who unites the country in adversity. The first was four years ago, when a divided America seemed hungry for the Bush of the 2000 campaign, the "compassionate conservative" who would govern from the center. He spurned that chance. The second came on Sept. 11, and he rose boldly to it, only to spend the unity he had forged on what proved to be a divisive war in Iraq.

The third opportunity begins tomorrow. A good start would be to reread the diary entry Bush's father wrote the day after his own inauguration. "We've got to find ways to do this compromise, 'kinder, gentler world.' "