For most of the 20th century, Santa Barbara County was a Republican stronghold. From 1920 to 1988, it was only carried by two Democrats: Franklin D. Roosevelt and Lyndon B. Johnson. However, the county has leaned to the left in recent years. Overall, Santa Barbara is a Democratic-leaning county in Presidential and congressional elections. The last Republican to win a majority in the county was George H. W. Bush in 1988. However, there is a dramatic difference in gradient between the "conservative" northern areas and the "liberal" southern areas of the county.
United States presidential election results for Santa Barbara County, California

Santa Barbara County has long been divided between competing political interests. North of the Santa Ynez Mountains, agricultural activities and oil development have long provided jobs. The northern portion also contains a large military base, Vandenberg Space Force Base, and thus military interests are prominent. These influences have created a Republican-leaning northern half.

On the other hand, the southern portion of Santa Barbara county has had an economy based on tourism, with a significant percentage of people with white-collar jobs, formerly in aerospace but more recently in software and other high-tech pursuits. Additionally, the University of California, Santa Barbara contributes to a liberal populace. The southern portion of the county has a strong history of left-wing activism, with anti-war protests common in Santa Barbara. It is generally believed that the inspiration for Earth Day was the 1969 Santa Barbara oil spill; however, Gaylord Nelson, the senator who proposed the idea, has never directly cited any direct cause for the establishment of the holiday.

On November 4, 2008, Santa Barbara County voted 53.5% against Proposition 8 which amended the California Constitution to ban same-sex marriages. It was the only county in Southern California to vote against it.