How did Dewey blow a lead so large (14 points) that pollsters like Elmo Roper decided in September to stop doing any more polls, declared Dewey the winner by a larger margin, and devoted himself to something more profitable? Let's see how Dewey measured up in these categories.
1. Authenticity: A remark attributed to the wife of a New York Republican politician would be widely repeated. "You have to know Mr. Dewey well", she said, "in order to dislike him." A farmer was asked about Dewey after the election and he said, "I kept reading about that Dewey fellow and the more I read the more he reminded me of one of those slick ads trying to get money out of my pocket."
3. Humility - His campaign train was filled with over 90 reporters who unanimously thought he would win and make an excellent chief executive, but they disliked him personally because of his haughty and aloof manner.
2. Self Management: One event on the campaign trail cost him dearly. The engineer of the train caused a lurch that knocked some bystanders to the ground. Dewey responded, "That's the first lunatic I've had for an engineer. He probably ought to be shot at sunrise ..."
4. Courage - His speeches were noteworthy for platitudes and a clear lack of controversy or new ideas. His goal was not to upset anyone, assuming that his large lead was safe and could only be threatened by risky challenges to the opposition. Dewey told Senator Robert A. Taft that when he got into controversies he lost votes - an observation Taft thought disgraceful.
Clearly Mr. Dewey exhibited all of the characteristics of a failed leader. Truman, on the other hand, was not liked very much by the press or the talking heads of his day, but he won over the average American with his straight talking and direct manner.
Check out Michael Hyatt's post about General George B. McClellan as described in Doris Kearns Goodwin's book Team of Rivals. He highlights five flaws to avoid that were characteristic of the leadership failure of this weak leader.