Having an atheist president would be a definite advantage. He would not be beholding to any group. He could introduce taxation on church property and income without a second thought...Halve the countries debt in a stroke. Any legislation that originates from religious delusions would be dismissed straight away....Saving millions in court costs..
An atheist is attractive because they use rational thought. They do not believe in supernatural causes but rather natural and rational causes. This is an advantage when making moral decisions, facts are better than make believe for the best decisions.
Atheism is the lack of belief in a god and is not a religion. However, it is protected and given the same rights as religion under the constitution because there was no other way to be fair to atheists but to grant them the same rights. So the courts used rational thought to produce fairness to atheists and protect them under the constitution. That was also moral.
What none of us needs is legislation which forces you to do what a religious person wants. The purpose of the constitution is to stop that from happening.
Personally I think that you should look at what sort of ideas and opinions that they are campaigning off of and less on the details of their personal life. A person should not be discriminated into not getting public office simple because he/she is gay, straight, Muslim, Jewish, or of course atheist.
If we're dealing with secular politics then religious views should not matter, if we're dealing with a country were religious laws are emulated politically then that is another story though I will take the assumption that you are talking about secular politics.
In that case then no because voting for someone based off of religious views completely contradicts with secular values. There is no correlation between rationality and atheism as rationality something that does not discriminate between religious views, their are many atheist leaders who've made irrational decisions based off of their anti religious views (take the Khmer Rouge and the French Reign of Terror for example) just as their have been religious leaders who've made rational decisions.
To simply put it: the question is irrelevant to secular politics.
I would need to know this person's stances and positions on various topics. I mean, the whole idea that every atheist is rational is a simply ignorant one. Many people come to the beliefs they have (especially this generation) due to looking at what all is presented to them. But no, I would not vote for anyone if they were atheist. Same goes for Christian, muslim, hindu, buddhist, and other.
Like Sam Harris, Richard Dawkins, Bill Maher etc then no. Their agenda and level of fundamentalism is akin to religious fundamentalism. Anyone who demonstrates this kind of strident set of beliefs show a basic inability to adjust their perspective relative to the situation. These types have reached their conclusion already, it's not the kind of person I would vote for.
If someone happened to be an atheist, agnostic or religious and weren't directed by these as to their view on a particular issue I would be more inclined to vote for them