Sonoma County is a sea of blue, reflecting the political bent that makes it the ninth-most liberal among California's 58 counties.
Sonoma and neighboring Mendocino County, at No. 8, are nearly tied on a political consultant's scorecard that puts nine greater Bay Area counties — and Los Angeles — on the top 10 list of most left-leaning counties.
Sparsely populated inland Northern California counties anchor the conservative list, and neither ranking is a surprise to anyone familiar with state politics.
But the California Political Precinct Index brings a detailed methodology to the blue vs. red ratings, using the votes on selected state ballot measures as an indicator of political ideology.
"It is indisputably valid," said Terry Price, a Santa Rosa political consultant. The index's scores are based on voting for "specific wedge issues," such as marijuana legalization and same-sex marriage, he said.
Moreover, Price and Herb Williams, another Santa Rosa political consultant, said the scores match their own experience in managing local political campaigns.
For example, the index identifies a portion of Santa Rosa — including the junior college, downtown, Proctor Terrace, McDonald Avenue and Railroad Square neighborhoods — as more liberal than the rest of the city.
"Those are the voters who elect progressive candidates," Price said.
Williams noted that areas surrounding Windsor and north of Healdsburg, rated as right-of-center by the index, formed the base that elected conservatives Nick Esposti and Paul Kelley to the county Board of Supervisors for three decades.
David Latterman, the San Francisco political consultant who compiles the index, acknowledged that his finding for Sonoma County is "not an earth-shattering conclusion."