Question: When did the senator who vacated a U.S. Senate seat which Thomas M. Davis considering a run for in 2008 serve as Secretary of the Navy?
Sentence (from "John Warner"): John William Warner (born February 18, 1927) served as Secretary of the Navy from 1972 to 1974 and as a five-term Republican United States Senator from Virginia from January 2, 1979, to January 3, 2009.
Relevant evidence: Yes