Rick Warren plays an old fallacy: false equation. He tries to turn "atheism" into an arrogance that says "I can lead a country all by myself." Edit: he says he could never vote for someone who "didn't believe in an authority greater than himself." But atheism simply means you don't believe in one possible authority greater than yourself, namely God. But an atheist seeking the presidency could still believe in plenty of authority above him/herself. The Constitution, for example. As is typical of guys like him, Warren can't see beyond his own blinders.
And here's Bill Maher responding to the issue of Candidates' faith with something refreshing. Rationality.