From a 2002 article in The Militant:
....The argument that there is such a thing as a "white vote" is a reactionary one. It reinforces ruling-class efforts to cajole working people who are not members of oppressed nationalities into thinking of themselves as "white" and to persuade them they have interests and concerns different from, and even hostile to, those of Blacks and other working people. It also fits in with the employers’ efforts to draw workers and farmers into identifying themselves as "Americans" with something in common with U.S. bosses.
Ideological purpose of the myth of race
The assumptions behind statements that "white voters" form a distinct social identity have no scientific value. The concept of race itself is a social construct of capitalist social relations, not a fact of biology.
These concepts, however, do serve an ideological purpose for the ruling class. The myth that there is a "white" nationality is promoted to divide working people and undermine solidarity with the struggles of oppressed nationalities against discrimination.
By contrast with this myth, the Black nationality is a fact; Black consciousness is a historic, progressive conquest. The Black nationality in the United States was forged by the course of development that capitalism took in this country following the defeat of Radical Reconstruction in the late 1870s, with the brutal, systemic oppression that was imposed on the Black population--and by the massive struggles led by Blacks against this oppression over much more than a century.
....In the 2000 elections, some of these forces sought to explain away the defeat of Albert Gore--who had already served for eight years as vice president of the world’s most brutal imperialist government--by claiming a Republican "coup." Unable to use such an argument in the 2002 elections, they are susceptible to blaming workers for the Republican election gains, while they themselves fall more and more into the "American" and patriotic framework of bourgeois politics today.