[True Grit]

I think it was Thomas Jefferson who said, the constitutional government we have established will only work for a moral, religious people.

[SeekAndFind]

That would be John Adams

See here:

http://www.johnadamscenter.com/home/why-john-adams/

EXACT QUOTE:

We have no government, armed with power, capable of contending with human passions, unbridled by morality and religion. Avarice, ambition, revenge and licentiousness would break the strongest cords of our Constitution, as a whale goes through a net. Our Constitution was made only for a moral and religious people. It is wholly inadequate to the government of any other.