in an episode of
Michael Shayne (1961) Denning was perhaps best known for his recurring starring roles in science fiction and horror films of the 1950s, and playing husband opposite
Lucille Ball on the radio series that led to
I Love Lucy in which he was replaced by
Desi Arnaz as Lucy's husband. Denning began acting in minor supporting and background roles through the 1930s and early 1940s until the start of World War II. According to Denning, his military service disrupted his acting career, and after his discharge it would be a year and a half before
Paramount Pictures offered him more acting work. During that time, he and his family lived in a mobile home that he alternately parked at
Malibu and
Palm Springs. Denning's unemployment ended when he was hired to star on the radio opposite
Lucille Ball in
My Favorite Husband. The
CBS Radio sitcom ran for 124 episodes from July 23, 1948, through March 31, 1951, and would evolve into the groundbreaking television sitcom
I Love Lucy. CBS wanted Denning to continue as the husband in the new sitcom but Lucille Ball insisted that her real life husband,
Desi Arnaz, play the part. The radio stint, however, led to a role on CBS television's series adaptation of
Mr. and Mrs. North. On television, he starred as the title character in the 1950 syndicated adventure series
Ding Howe and the Flying Tigers. He was cast as Dr. Greg Graham in the 1959 series,
The Flying Doctor. He also starred as the title character in the detective series
Michael Shayne (1960–1961) and shared title billing with
Barbara Britton in the detective series
Mr. and Mrs. North (1952–1954). In 1964-1965, Denning played Steve Scott in the comedy series
Karen. In later life, he had a recurring role as the fictitious governor of Hawaii, Paul Jameson, in the
CBS television
crime drama series,
Hawaii Five-O (1968–1980), starring
Jack Lord. He appeared three times on the
ABC religion
anthology series Crossroads, as Dr. Ira Langston in "Chinese Checkers" (1955) and as the Reverend George Bolton in "The Bowery Bishop" and as the Reverend Lloyd E. Williams in "The Pure White Orchid" (both 1956). In other activity on
radio, Denning played Uncle Jack in ''
It's a Crime, Mr. Collins (1956-1957) on the Mutual Broadcasting System. He also was the second actor to play Jerry North in the radio version of Mr. and Mrs. North''. Denning later appeared in several 'B' crime drama films before starring in science fiction and horror films. In 1957, he began the first of a series of television appearances, usually as a supporting character, though he did star briefly in two television dramas,
The Flying Doctor (1959), and
Michael Shayne (1960–61). In 1968, Denning completed his last film, a comedy titled
I Sailed to Tahiti with an All Girl Crew. Semi-retired and living on the island of
Maui with his wife, Denning was contacted by producer
Leonard Freeman, who offered him the supporting role as the governor of Hawaii in the TV detective series,
Hawaii Five-O. In order to persuade Denning to sign on in the recurring role, Freeman guaranteed Denning five-hour days and a four-day work week. ==Recognition==