The below image popped up on Facebook apparently alleging that Roger Ailes, president of the Fox News Channel, said:
"The truth" is whatever people will believe.
The peculiar placement of the quote marks makes it unclear whether this is intended as a direct quote attributed to Roger Ailes or is just commentary.
Google reveals that Joseph Heller said something very much like this in his 1984 book God Knows:
"The truth is whatever people will believe is the truth. Don't you know history?"
But I can find no reference to Roger Ailes having said this, or anything substantially similar.