We've been to some small towns and heard us some big talk, and tonight in Iowa, we begin to get a little closer to the real thing. We've heard a lot about how personal ambition shapes character for better and worse. Are the candidates for president trying too hard? Have they been seeking power too long? Are they in the race for us, or for them?

Most of the analysis has been candidate-specific, without much talk about what it actually takes to be a great president, or even a good one. It's still hard to tell who will begin to separate from the pack tonight. That's often how it works in a democracy. We not only fail to foresee the winners, but have trouble discerning who's likeliest to rise to the occasion inside the confusing fog of troubling events. Most of us who cover the race evaluate and analyze what's both lofty and trite, but we shy from those old-fashioned standards by which we measure excellence.

Robert Faulkner, a professor of political science at Boston University, reminds us in his fortuitous new book that it's important to think hard above the fray, to consider what informed leadership in the past to inform what we expect of leaders in the future. In "The Case for Greatness: Honorable Ambition and Its Critics," he reaches back as far as Aristotle for the standards of leadership, to accurately measure who has the qualities of excellence.

"Magnanimity" and "greatness of soul" applaud ambition as the natural growth of virtue, compelling us to do good because doing good is the right thing to do. You can find these qualities in Nelson Mandela and Margaret Thatcher. We cherished it in Abraham Lincoln, who defined his own ambition with humility when he first ran for public office at the age of 23. "I can say for one that I have no other [ambition] so great as that of being truly esteemed of my fellow men, by rendering myself worthy of their esteem," he said. "How far I shall succeed in gratifying this ambition is yet to develop."

But develop it did. It was what Frederick Douglass, the one-time slave and eloquent abolitionist, saw in Lincoln when he met him for the first time in 1861: "He was the first great man that I talked with in the United States freely, who in no single instance reminded me of the difference between himself and myself, of the difference of color." That quality may be easier to find today, but it's difficult enough. The appeal of Barack Obama, it seems to me, is that he wants to see others and be perceived by others as no different from others, that the color of his skin is irrelevant. He's the first black politician to suggest this is possible. How far Obama can succeed is "yet to develop," but even in his inexperience he suggests he has that potential.

John McCain is another candidate who is truly esteemed by rendering himself worthy of it. That's evident in the fortitude and heroism he showed in a brutal Vietnamese prison camp and in his stake in ideas he believes to be right, even when such ideas cost him the support of his party. Joe Lieberman is another whose ambition encompasses magnanimity and explains why he supports John McCain for president although he's of another party.

Magnanimity for Aristotle required pride based on virtue, public and private, and it grew out of both personal and patriotic attitude, fusing the inside gentleman with the gentleman we see on the outside. "The person who seems to be great-souled is one who considers himself worthy of great things and is worthy of them," wrote Aristotle.

This is particularly difficult to identify in our celebrity culture. We not only expect our presidential candidates to campaign with showbiz celebrities, but to appear to be showbiz celebrities themselves. The Clintons are the model. Michelle Cottle observes in the New Republic that the Clintons "have passed some point where they're no longer just politicians. They're rock stars." That seems to be why the bad things they do don't stick. We expect trashy behavior from celebrities.

If magnanimity is difficult to elicit in the current political culture, it's nevertheless something we should seek in our candidates. True esteem in a leader should mean that he is worthy of such esteem. Nobody is entitled to a pass, in Iowa or elsewhere.