Bounce/No Bounce

Political Figures: Senator John Kerry (D-Massachusetts)
FOX News/Opinion Dynamics Poll. Aug. 3-4, 2004. N=900 registered voters nationwide. MoE ± 3.
8/3-4/04 52% Favorable 34% Unfavorable
7/20-21/04 44% Favorable 39% Unfavorable

But there was "no bounce"?