An FBI memo dated June 17, 1958 provides that "on June 4, 1958, after he had won the California Democratic primary as a candidate for Governor, California Attorney General Edmund Pat Brown received a message of congratulations" from Wilbur Clark and Hank Greenspun "which read as follows" in full:
The country is in need of great leadership. Your outstanding victory in the primaries is a spark which will catapult you into the White House. We rejoice with you. Wilbur Clark and Hank Greenspun.
The FBI notes that "both Clark and Greenspun hold interests in Las Vegas, Nevada, hotels and are carried as top hoodlums by the Salt Lake City Office."
Brown served as California governor from 1959 to 1967 but the White House eluded him.
Further reading that may be of interest: