J. Edgar Hoover was a Republican. Hoover maintained strong support in Congress until his death at his Washington. he was also instrumental in founding the FBI in 1935. Check out http://en.wikipedia.org/wiki/J._Edgar_Hoover to read more about him.
Hoover was a Democrat, not a Republican. He was appointed by a Democratic president- and was a man of the south. During and before the civil rights era, Republicans did not hold power in southern states... Which were blue.