I am not entirely positive and perhaps the other forum members can provide insight, but I believe the numbers that rejected evolution used to be much higher? As high as 50% at one point.
I think that that just depends on how you add the figures together. After all, the same number that gave us "One-third of Americans reject human evolution" could also with equal validity give us "One-third of Americans agree with Darwinism". You've got that wishy-washy block in the middle that apparently agree with the fact of evolution but reject the theory of evolution, so whether you could them as pro or anti depends on exactly what you're counting.