No politician, least of all the President of the United States, can afford to deny what science informs us about reality. Politicians who do this cannot be trusted to come to accurate conclusions about technological and scientific problems or issues, cannot be trusted with leadership of a nation that depends upon science and technology, and cannot be trusted to do a good job at separating evidence from personal faith.
Lawrence Krauss writes in New Scientist about this problem:
'Let's take scientific literacy. [Arkansas Governor Mike] Huckabee, for example, openly stated that he does not know if the Earth was created in six days, 6000 years ago. This represents a remarkably open mind in the face of overwhelming evidence that it was not. This point is no more unresolved than the question of whether the Earth is round, or whether it goes round the sun.
If a potential president is unwilling to accept the fundamental results of chemistry, physics, biology, astronomy and geology, all of which tell us that a six-day creation is incompatible with everything we know about the world, and all the principles on which we base modern technology, then how can that individual be expected to assess the complex scientific and technological issues that will form the basis of US policy over the next eight years? Those who reject evolution owe the country an answer to that in the upcoming debate.
There is also the question of leadership. The US remains at the forefront of the technological world thanks to generations of scientific leadership. As many have pointed out, this is now in jeopardy, in part because the country is not doing a good enough job of educating the technical workforce needed to man the economic engines of the 21st century.
Finally, and most fundamentally, there is the distinction between beliefs and evidence. Three candidates have spoken in the debates so far to explain their views on evolution: Brownback, Huckabee and Arizona senator John McCain, who had stated that he believes in evolution but later congratulated Huckabee on his statements, including that "if anybody wants to believe they are descendants of a primate they are certainly welcome to it".
All three answered the evolution question as if it was a religious point, rather than a scientific one. ...The candidates' confusion on this matter is serious, and we should worry about it a great deal in a would-be commander-in-chief. Whether the issue is descent of species, weapons of mass destruction or human-induced global warming, we may believe what we want, but if we ignore the evidence we can be wrong in ways that can have manifest and serious consequences.
Science is not mere storytelling. It makes predictions that help us to control our destiny. The actions of the president and indeed any politician should be based on the best possible evidence, not a priori beliefs, whether they are ideological or religious. Our future depends on it.'
When we elect a president — or any politician for that matter — we have to assume that they will face questions, issues, and problems which they haven't quite faced before. This means that in choosing a politician, we can only rely partially on their past history and what they say about their general policies. More important is their overall character and their ability to make sound decisions, their reasoning skills, and their overall intellectual character. This is what will tell us about how they do when they are faced with new problems.
If someone is in denial about reality and science because they think it conflicts with their religious ideology, how can we trust them to fairly, reliably, and reasonably deal with new scientific or technological issues they face?