This is the CNN sample
Mitt beats Obama on favorable/unfavorable by a wide margin pre debate
That is just not consistent with any poll I have seen

4. Do you have a favorable or unfavorable opinion of Barack Obama?
(Post Debate) (Pre-Debate)
Oct. 3 Sept. 28-Oct. 2
2012 2012
Favorable opinion 49% 49%
Unfavorable opinion 49% 50%
No opinion 2% 1%

5. Do you have a favorable or unfavorable opinion of Mitt Romney?
(Post Debate) (Pre-Debate)
Oct. 3 Sept. 28-Oct. 2
2012 2012
Favorable opinion 56% 54%
Unfavorable opinion 42% 42%
No opinion 2% 3%