As of the census of 2000, there were 3,770 people, 1,496 households, and 1,036 families residing within the city limits. The population density was 262.7/km² (680.4/mi²). There were 1,737 housing units at an average density of 121.1/km² (313.5/mi²). The racial makeup of the city was 87.72% White, 1.19% African American, 1.14% Native American, 4.19% Asian, 0.66% Pacific Islander, 1.33% from other races, and 3.77% from two or more races. Hispanic or Latino of any race were 4.35% of the population.
There were 1,496 households out of which 32.1% had children under the age of 18 living with them, 52.9% were married couples living together, 12.4% had a female householder with no husband present, and 30.7% were non-families. 25.5% of all households were made up of individuals and 10.1% had someone living alone who was 65 years of age or older. The average household size was 2.48 and the average family size was 2.96.
In the city the population was spread out with 26.5% under the age of 18, 6.9% from 18 to 24, 26.4% from 25 to 44, 25.7% from 45 to 64, and 14.4% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 94.5 males. For every 100 females age 18 and over, there were 90.2 males.
The median income for a household in the city was $36,900, and the median income for a family was $45,056. Males had a median income of $36,381 versus $23,561 for females. The per capita income for the city was $20,333. About 10.2% of families and 15.5% of the population were below the poverty line, including 16.6% of those under age 18 and 8.3% of those age 65 or over.
In the 2004 US presidential election, Blaine cast 49.33% of its vote for Democrat John Kerry and 50.67% for the winner, Republican George W. Bush.