Even in an economic recession, Americans in urban areas continue to buy second homes in rural parts of the country, frequently helping to revitalize depressed areas. Inevitably, though, political operatives have also been seizing on weekend residents as a way to change the political complexion of rural communities.

Nowhere is the battle being more fiercely fought than in New York's Columbia County, a two-hour drive up the Hudson River from New York City. Local Democrats have encouraged weekend residents to register and vote...