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."
"It's a perfectly respectable liberal county," said Latterman, who is associate director of the University of San Francisco's Leo T. McCarthy Center for Public Service and the Common Good.
Sonoma County voters favored legalizing marijuana in 2010 and rejected a ban on same-sex marriage in 2008 — in both cases running counter to the statewide vote — and have not elected a Republican state or federal legislator since 1996.<NO1><NO>
The county didn't match Bay Area liberal hotbeds like San Francisco, Alameda and Marin counties, which posted three of the top four liberal scores in the 2012 update of Latterman's index.
"But who does?" Latterman said.
<NO1><NO><NO1><NO>Overall, the county's most liberal <NO1><NO>areas, with index scores in the 70s, <NO1><NO>are within the cities and scattered throughout west county and along the Russian River.
Suburban and rural areas outside cities are generally less liberal in the rest of the county, a pattern that Latterman said is repeated throughout the state.
Route 99 in the Central Valley runs through a solidly red political landscape, punctuated by liberal blue pockets in cities like Fresno, Modesto and Bakersfield.
Sonoma and Mendocino counties scored in the low 60s on a scale of zero to 100, with zero the most conservative, both well above the statewide score of 56.3.
The ideological midpoint of the index is 50.
One of Mendocino's precincts scored a midnight blue 100, the highest in the state, while a Kern County precinct earned a rock-ribbed red zero.
Lake County scored a 55.5.
Latterman developed the current index by crunching election results in more than 20,000 precincts statewide, using the votes on nine selected ballot measures in 2008 and 2010.