Cogdill was first elected to public office in 1975 as a member of the Board of Directors of the Bridgeport Fire Protection District in Mono County.
In 1979, he moved to Modesto, where he would build his real estate appraisal business. He would live there for the remaining 38 years of his life.
He had served on various boards and commissions in both the public and private sectors, including two terms on the Modesto City Council.
Prior to being elected to the Senate, Cogdill represented the 25th District for six years in the California State Assembly. During that time, he served as Vice Chair of the Rules Committee. Cogdill also sat on the Budget, Agriculture, and the Joint Legislative Audit Committees. Additionally, Cogdill acted as the Assembly Minority Floor leader and was responsible for coordinating Republican efforts on the Assembly Floor.
In 2006, Cogdill was elected to the State Senate to represent the 14th District, which comprised all or a portion of Fresno, Madera, Mariposa, San Joaquin, Stanislaus and Tuolumne Counties.
Upon his election, Cogdill was named Vice Chair of the Public Safety Committee, the Revenue and Taxation Committee, and the Joint Legislative Audit Committee. He was also named a sitting member of the following committees: Budget and Fiscal Review; Budget Subcommittee on Health and Human Services; Elections, Reapportionment and Constitutional Amendments; Human Services; Natural Resources and Water; Select Committee on Air Quality; and Joint Legislative Budget. Additionally, he was named as the Senate Minority Caucus Whip, a Republican leadership position responsible for coordinating Republican activities on the Senate Floor.
In the Senate, Cogdill focused his efforts on economic development, strengthening public safety, keeping taxes low, improving air quality, and expanding water supply and storage opportunities. He worked to prevent increased taxes and regulations on businesses and agriculture. During his time as Chair of the California State Legislature Rural Caucus, he worked on access to health care and quality education.
With his election as Senate Republican Leader in 2008, Cogdill stepped down as Vice Chair of the Public Safety Committee (although he did remain a member of the committee); switched from the Budget Subcommittee on Health and Human Services to the Budget Subcommittee on Resources, Environmental Protection and Energy; and left the Human Services Committee. He was succeeded as Caucus Whip by Senator Tom Harman. His other committee assignments and vice chairmanships were unchanged.
Shortly after midnight on the morning of February 18, 2009, after several days of late-night, contentious debates over closing a $42 billion gap in the state budget, Senate Republicans met in caucus where they voted to replace Cogdill with State Senator Dennis Hollingsworth. This removal was precipitated by Cogdill's agreement to join with Democrats as a member of the "Sacramento Six" to raise vehicle license fees and taxes during the administration of Governor Arnold Schwarzenegger.
Despite serving in the Senate only eleven months in 2010, Cogdill was the second largest taxpayer-funded gas card spender in the Senate for 2010 costing $5,941.26
Rather than seek re-election to the Senate in 2010, Cogdill ran for Assessor of Stanislaus County. He would serve as Assessor from January 2011 until his October 2013 resignation.
In October 2013, Cogdill resigned as Stanislaus County Assessor to become president and CEO of the California Building Industry Association, a post he held until his death. Cogdill previously received campaign contributions from the CBIA during his time in the Legislature.
With his wife of 47 years, Stephanie, Cogdill had two children, David Jr. and Meghan. Cogdill died of pancreatic cancer on July 23, 2017.Friend of the Year Award by the Hispanic Chamber of Commerce
President's Award by the Stanislaus County YMCA
"One Voice" Award by the Sacramento/Fresno Council of Governments
Leadership Award by the Greater Area Fresno Chamber of Commerce
"E" Award for Excellence by Leadership Modesto, an affiliate of the Modesto Chamber of Commerce
Legislator of the Year for 2005 by the Associated Builders and Contractors
Patti Mattingly Distinguished Legislative Award by the Regional Council of Rural Counties
Assembly Member of the Year for 2003 and 2005 by the California State Sheriffs’ Association
Legislative Leadership Award by the California Rural Health Association
Legislator of the Year for 2003 and 2004 by the California Forestry Association
Legislator of the Year by the California Mobilehome Parkowners’ Alliance
Legislative Special Recognition Award by the Veterans of Foreign Wars
Legislator of the Year by the California Women in Timber Association
Modesto Man of the Year by the Veterans of Foreign War
Distinguished Service Award by the Future Farmers of America
Golden Trout Award for 2006 by California Trout
Profile in Courage Award for 2010 by the John F. Kennedy Library Foundation