Because he treats listeners as if they are smart.

That is the significance of "They want us to think" and "The strongest argument is" and "The arithmetic says one of three things must happen" and even "Now listen to me here, this is important." He is showing that he understands the many layers of logic and evidence and positioning and emotion that go into political discussion -- and, more important, he takes for granted that listeners can too.

The main other place you hear discussion based on the same assumption that people of any background, education level, or funny-sounding accent can understand sophisticated back-and-forth of argument and counter-claim is sports-talk radio. ("I understand the concern about Strasburg's arm. But ... ") You hear insults and disagreements and put-downs on sports-talk discussions. You rarely hear the kind of deliberate condescension, the unconcealable effort as if talking to slow learners, of many political "authorities" addressing the unwashed.

It's the difference between clarifying, and over-simplifying. Clarification, with the confidence that people can understand the back and forth, lies behind passages like this, which characterized most of the speech. Emphasis on the parts that show his approach being applied:



We Democrats, we think the country works better with a strong middle class, with real opportunities for poor folks to work their way into it, with a relentless focus on the future, with business and government actually working together to promote growth and broadly shared prosperity. You see, we believe that "We're all in this together" is a far better philosophy than "You're on your own."



(APPLAUSE)



So who's right? Well, since 1961, for 52 years now, the Republicans have held the White House 28 years, the Democrats 24. In those 52 years, our private economy has produced 66 million private- sector jobs. So what's the job score? Republicans: twenty-four million. Democrats: forty-two.



(APPLAUSE)



Now, there's -- there's a reason for this. It turns out that advancing equal opportunity and economic empowerment is both morally right and good economics. Why? Because poverty, discrimination, and ignorance restrict growth.



(APPLAUSE)



When you stifle human potential, when you don't invest in new ideas, it doesn't just cut off the people who are affected. It hurts us all.



(APPLAUSE)



We know that investments in education and infrastructure and scientific and technological research increase growth. They increase good jobs, and they create new wealth for all the rest of us.



(APPLAUSE)



Now, there's something I've noticed lately. You probably have, too. And it's this. Maybe just because I grew up in a different time, but though I often disagree with Republicans, I actually never learned to hate them the way the far right that now controls their party seems to hate our president and a lot of other Democrats.



(APPLAUSE)



I -- that -- that would be impossible for me, because President Eisenhower sent federal troops to my home state to integrate Little Rock Central High School. President Eisenhower built the interstate highway system. [etc]



Or



Now, when Congressman Ryan looked into that TV camera and attacked President Obama's Medicare savings as, quote, "the biggest, coldest power play," I didn't know whether to laugh or cry...



(LAUGHTER)



... because that $716 billion is exactly to the dollar the same amount of Medicare savings that he has in his own budget!



(APPLAUSE)



You got to give one thing: It takes some brass to attack a guy for doing what you did.



(LAUGHTER)



(APPLAUSE)



Now -- so -- wait a minute.



(APPLAUSE)



Now you're having a good time, but this is getting serious, and I want you to listen.



(LAUGHTER)



It's important, because a lot of people believe this stuff. Now, at least on this issue, on this one issue, Governor Romney has been consistent. He...



Different people have different natural modes for their speech, and not many people can pull it off just the way Clinton does. But Clinton reminds us of the value (and rarity) of this tone in politics -- and the next time you listen to a sports-talk channel, think how much better our political discussion would be if participants assumed as much sophistication about argument as ESPN and radio-talk hosts do.





Update: I've just seen

: I've just seen Molly Ball's assessment of Clinton's efforts to reason and persuade, which observed similar strengths in his approach.