The growing, or at least persistent, power of municipal governments has the effect of turning naturally Blue cities even more azure. Most private-sector employees in New York City backed Mike Bloomberg; most public employees voted for Democrat Mark Green. Bloomberg's anti-tax, anti-spending campaign was a direct threat to the jobs of many city workers, who feared having to find new ways of earning their living. Because their jobs are on the line in every election, government workers are especially mobilized in politics: Although they account for only a third of the workforce in New York, Malanga notes, public sector employees represented 37 percent of the electorate in 2001.
If you think that's just a New York City problem, consider the power of the prison guards' union in California.