Was during the debate.
http://elections.nytimes.com/2008/president/debates/transcripts/vice-presidential-debate.html...
BIDEN: Well, again, I believe John McCain, were he here -- and this is a dangerous thing to say in the middle of an election -- but he would acknowledge what I'm about to say.
I have been able to work across the aisle on some of the most controversial issues and change my party's mind, as well as Republicans', because I learned a lesson from Mike Mansfield.
Mike Mansfield, a former leader of the Senate, said to me one day -- he -- I made a criticism of Jesse Helms. He said, "What would you do if I told you Jesse Helms and Dot Helms had adopted a child who had braces and was in real need?" I said, "I'd feel like a jerk."
He said, "Joe, understand one thing. Everyone's sent here for a reason, because there's something in them that their folks like. Don't question their motive."
I have never since that moment in my first year questioned the motive of another member of the Congress or Senate with whom I've disagreed. I've questioned their judgment.
I think that's why I have the respect I have and have been able to work as well as I've been able to have worked in the United States Senate. That's the fundamental change Barack Obama and I will be bring to this party, not questioning other people's motives.