Wrapped in the Flag and Carrying the Cross

There is a quote commonly attributed to Sinclair Lewis: “When fascism comes to America, it will be wrapped in the flag and carrying the cross.”

But to my knowledge there's no citation behind that quote.

What I did find, though, is this New York Times summary of a sermon preached by Methodist minister Howard E. Luccock, at Riverside Church in New York City on 11 September 1938.