Many people will argue in defense of candidates that neither a candidate's race, gender, nor religion matters.
I agree that race and gender do not matter. In some contexts, perhaps they may--at least a little. However, in the context of the United States, I suggest that they matter as much as if a candidate enjoys boxers or briefs--of course if gender is the issue, then that may very well be an interesting (perhaps even significant) issue.
Religion, on the other hand, matters. A religious man (or woman) can be good. Indeed, a religious man or woman should be good.
That said, there is also a danger inherent in powerful and religious people. Need I list the examples?
Of course nonreligious people also have accounted for much grief to this world's history, but look closely at them. Hitler's Nazism was essentially religious, as was Lenin and Stalin's Bolshevism.
Blind devotion to anything and a willingness to destroy all opposition is dangerous in all forms, whether it wears a cross, a yamaka, orange robes, paramilitary tunics, or suicide bombs.
Let's look a Barack Obama. For twenty years, he belonged to Jeremiah Wright's congregation (I decline to call him a reverend). Now either Obama believes in Wright's outrageousness, or he doesn't.
If Obama is truly a follower of Wright (and is only distancing himself from the false prophet for political reasons), then Obama is a dangerous man.
If Obama doesn't really believe the kind of things that Wright utters, then why was he a parishioner for so long? The only good answer is that Obama doesn't really believe anything in terms of religion, and that he only went to church to make himself appear a religious man so that he could one day run for president.
The latter may actually make Obama even more dangerous than the former.
As for McCain, he's just useless. Not dangerous, just useless. Enough said.