Sanders has not actually proclaimed himself to be an atheist. He definitely is not a communist and is merely irreligious, not anti-religious. (Note his fight for the Chabad menorah in Burlington — while that state’s Jewish governor wanted to cave to the ACLU. It would be peculiar for an atheist to make a bracha to a God he believes does not exist!)
Leon Blum was Prime Minister of France, not the Head of State. Pierre Mendes-France, also Jewish, was also Prime Minister of France. Blum got France to arm itself to the teeth against the Nazi threat and Mendes-France helped Israel a lot.