Mark Shields on Newshour: "It cheapens Bill Clinton. He's a smaller man as a result of this campaign. "

Bill Clinton has quite simply made a fool of himself with his cheap and personal attacks on Sen. Barack Obama. He should be ashamed of himself--except that he has shown over and over again that he has no shame. He has simply not conducted himself in a manner fit for a former President--more like a really mean-spirited petty political boss who resents any challenge to his authority.

Bill Clinton's campaign effect

JIM LEHRER: We've got just a minute or so left here. Bill Clinton, there've been all kinds of stories in the last couple of days about the role he is playing. Do you have a comment on this?
DAVID BROOKS: I think, in theory, he is entirely positive. In practice, he's mostly negative.

People like the idea of Bill Clinton. He's still popular, especially among Democrats, extremely popular. But when he's actually campaigning, when you see a former president attacking another candidate or condescending to another candidate, I think it has an entirely negative cast.

MARK SHIELDS: Contrast him with George H.W. Bush, whose son ran for president, and Clinton's wife. He only served the purpose of being a character reference for his son in specific instances in the 2000 campaign, very selectively, very discriminatingly used.

It cheapens Bill Clinton. He's a smaller man as a result of this campaign. David is right.

And I just think -- he got a call from a member of Congress, a very close friend, who said, "Mr. President, you're behaving like a precinct committeeman, a captain out there."

JIM LEHRER: He's getting angry, too, isn't he?

MARK SHIELDS: Well, he is. And he's a man that's done big things, I mean, with George Herbert Walker Bush, since his presidency, you know, with the tsunami and his AIDS efforts.

But I have to say, I mean, his temper, which was legendary in the White House, but only seen by the staff, now is being seen by people, you know, on YouTube and on the campaign trail.

JIM LEHRER: You think it's a negative or a plus?

DAVID BROOKS: A clear negative. I agree. He's demeaned it. And he's demeaned Hillary. He's caused Hillary all sorts of problems.

JIM LEHRER: OK, thank you all.