Bill Kristol warns John McCain that biography is not enough and that McCain would do well to flesh out his domestic agenda. That is sound advice, but McCain’s use of biography, I think, is really an argument about character, which is becoming an increasingly more important part of the campaign as we learn more and more about Barack Obama.

In opening his Bio Tour today, McCain spent quite a bit of time talking about his family’s history of military service, but more importantly, what that background imparted to him:

Like most people, when I reflect on the adventures and joys of youth, I feel a longing for what is lost and cannot be restored. But though the happy pursuits of the young prove ephemeral, something better can endure, and endure until our last moment of life. And that is the honor we earn and the love we give when we work and sacrifice with others for a cause greater than our self-interest. For me that cause has long been our country. I am a lucky, lucky man to have found it, and am forever grateful to those who showed me the way. What they gave me was much more valuable and lasting than the tribute I once paid to vanity.

I am the son and grandson of admirals. My grandfather was an aviator; my father a submariner. They were my first heroes, and their respect for me has been one of the most lasting ambitions of my life. They gave their lives to their country, and taught me lessons about honor, courage, duty, perseverance and leadership that I didn’t fully grasp until later in life, but remembered when I needed them most. I have been an imperfect servant of my country for many years. But I am their son, and they showed me how to love my country, and that has made all the difference for me, my friends, all the difference in the world.

I think it’s clear that McCain will again and again come back to themes which differentiate him from Obama (e.g. selflessness vs. egotism, integrity vs. opportunism, courage vs. calculation, devoted patriotism vs. multicultural skepticism). Obama’s got the Obama girls, but McCain’s got the McCain boys.

So, yes, it is important for McCain to develop some policy initiatives, but in a race where some of the main concerns surrounding his likely opponent are about character and gravitas, McCain is going to do everything he can to remind voters of the differences between the two.