Who said when America ceases to be good she ceases to be great?

Alexis de Tocqueville - the full quote is:

"I sought for the key to the greatness of America in her harbors; in her fertile fields and boundless forests; in her rich mines and vast world commerce; in her public school system and institutions of learning. I sought for it in her democratic Congress and in her matchless Constitution. Not until I went into the churches of America and heard her pulpits aflame with righteousness did I understand the secret of her genius and power. America is great because America is good, and if America ever ceases to be good, America ceases to be great."