Evolution a majority - Creation, even more so!

An aquaintance provided me with the results of a July 2007 Gallup poll that gave the following results:

Evolution, that is, the idea that human beings developed over millions of years from less advanced forms of life

Definitely true

Probably true

Probably false

Definitely false

No opinion

Total true

Total false

18

35

16

28

3

53

44

Creationism, that is, the idea that God created human beings pretty much in their present form at one time within the last 10,000 years

Definitely true

Probably true

Probably false

Definitely false

No opinion

Total true

Total false

39

27

16

15

3

66

31

What are we to make of these results? The positions staked out in these two questions are worded in a way as to make them mutually contradictory. Yet we have 53% of those polled favoring evolution on the one hand - and then 66% polled favoring creation on the other!
I suspect there must be some kind of polling bias that causes interviewees to disproportionately agree with statements that are posed to them. I haven't heard of such an effect, but how else to make sense of this data?

A second observation is that the ratio of 66% recent-creation, to 53% evolution, is consistent with the other poll data I've discussed. One mystery would be how old-earth creationists would answer this question. Indeed, old-earth creationists might be inclined to agree with each of these questions, which might explain the discrepancy noted above. But this would only explain it if the proportion of young-earth creationists has grown even more rapidly in recent years, which is an unsupported assumption at this point.

Another finding of the Gallup poll, oddly enough, was that 15% of those polled would be more likely to vote for a candidate who rejects evolution, versus 30% who would be less likely. Apparently the average creationist does not value the foundational importance of creationary belief as much as evolutionists, for whom this issue is more of a litmus test. This is consistent with observations that modern Christians and other creationary communities have become very shallow and superficial in their understanding of their theistic worldview.

Another possibility would be that voters perceive belief in evolution as being more 'sophisticated' or something along those lines, and are concerned that those who reject evolution might lack the skills/knowledge/experience to be a good political candidate. This would be a surprise to the Founding Fathers!