But, as Sunday’s contrast made clear, Obama still seems like a human being. He still seems to return each night to some zone of normalcy where personal reflection lives. He wasn’t fully candid when answering questions about the Rev. Jeremiah Wright, but there are some inner guardrails that prevent the spin from drifting too far from the truth. Thoughtful and conversational, he doesn’t seem to possess the trait that Clinton has: automatically assuming that critics are always wrong.

Obama still possesses his talent for homeostasis, the ability to return to emotional balance and calm, even amid hysteria. His astounding composure has come across as weakness in the midst of combat with Clinton, but it’s also at the core of his promise to change politics. He vows to calm hatred and heal division.

This contrast between combat and composure defines the Democratic race. The implicit Clinton argument is that politics is an inherently nasty business. Human nature, as she said Sunday, means that progress comes only through conquest. You’d better elect a leader who can intimidate. You’d better elect someone who has given herself permission to be brutal.

Obama’s campaign grows out of the longstanding reform tradition. His implicit argument is that politics doesn’t have to be this way. Dishonesty and brutality aren’t inevitable; they’re what gets in the way. Obama’s friend and supporter Cass Sunstein described the Obama ideal in The New Republic: “Obama believes that real change usually requires consensus, learning and accommodation.”

That’s regarded as naïve drivel in parts of Camp Clinton.

Campaign issues come and go, but this is a thread running through the race. One believes in the raw assertion of power, the other the power of communication.

They are imperfect messengers for their creeds. Clinton rails against “Wall Street money brokers,” but her policies are often drawn from the Wall Street wing of the party. Obama talks about postpartisan compromise in the abstract, but rarely in the particular.

Still, amid the storms of the presidency, their basic worldviews would shape their presidencies. Obama is instinctively a conversationalist and community-mobilizer. Clinton, as she says, will fight and fight. If elected, she’ll have the power to take the Hobbesian struggle she perceives, and turn it into remorseless reality.