Presidential debates are a two part game. There is the short term issue where pundits declare winners and then there is a the term goals. One of the major things that come from the debate is people get to see how each candidate conducts themselves. What they are most looking for is the ability to carry one's self like a President.
In that regard Mitt came up short, very short. Mitt came across to the American people like a used care salesman. All that was missing was the gold chains and a cheap suit. Mitt did not have the bearing of a President. People expect Presidents to be open, honest and calm. They expect that they will carry themselves not a member of the cast of the New Jersey House Wives.
Mitt evasiveness on details has the same "I am being conned" feel that one gets when you ask the used car salesman if there are any mechanical problems with the car and the salesman ignores your question and points out how fast the car can drive.
Beyond the smarmy I am trying to put one over on you bearing, Mitt managed to throw in that rich elitist attitude. Mitt dismissed the moderator like he was Mitt's private butler. That sort of contemptuous attitude toward people in a lower position does not play well in America.