I think its pretty important for a candidate to have some knowledge of how science works and what the prevailing scientific understanding of our world is.
In fact, I wish we knew more about all of our candidates scientific literacy.
Well, it may be important but why is it so for the office of the presidency? Did JFK really need to know or have some rudimentary knowledge of quantum physics in dealing with Khruschev? Was knowledge and understanding of the "Origins of Species" going to guide him to a peaceful resolution of the Cuban missile crisis? Is there something equivalent to the idea of a "Bible Code" in scientific claims which, if decyphered, will provide infallible wisdom and guidance when dealing with terrorists, the Cuban missile crisis, and so forth? I seriously doubt it.
The Office of the Presidency of the United States is first and foremost a political office, dealing exclusively with foreign and domestic affairs. The Office of the Presidency is not one in which the president invites heads of state to D.C. so they can determine whether the God-particle exists, how it can be found, why it has eluded our detection thus far, whether the LHC (Large Hadron Collider) atom smasher in Europe will locate it, the various fields of existence, a mass field, electron field, how E=mc2 means the energy in existence at the beginning has to be equivalent to the energy in existence now, and so forth. The Office of the Presidency is not the equivalent to being a member of the Manhattan Project or a member of the scientific community.
The Office of the Presidency is a political office, not a scientific one, and consequently, I want to know how and why this knowledge, I concur is important, is so essential to being a good president? I wonder how many of our presidents were largely ignorant of science? I wonder how much science Pres. Lincoln knew, FDR, Teddy, JFK, Wilson, McKinley, and the others considered "good" or "great" executives?
Why is scientific literacy a litmus or the litmus test? I can conceive of more important knowledge, such as analytic and critical thinking skills, a good grasp of U.S. history and world history, economics, both globally, domestically, and their interrelationship, law, domestic and international law, along with diplomacy skills, temperment, and so forth.
If they are generally bright, smart, and intelligent in these areas, then I am willing and it is easier to dismiss those areas of obstinance where they do not accept some proposition as true, despite the prevailing evidence in support of it.
I think Sara Palin satisfies this nicely. She has been a small business owner and we have not yet heard of her making any crazy, insane, or nuts decisions while mayor or governor in Alaska. Maybe such reports have yet to be dissemminated, reports where the only sense to be made of her decision was because of her devotion to God, the Bible, or some religious belief but in the absence of such evidence, I think we can justifiably assume she will not be some cazed leader, like Nero or Caligula.