Keep in mind that the anti-racist conservative wouldn't be that different from your typical republican candidate. He'd still be anti-gay, anti-abortion, pro-war, etc.
The racist liberal would still be 'green', pro-choice, pro-welfare, etc and all the other trendy causes. He just doesn't think overly highly of the dusky hued peoples of the world.
Why so sure about a landslide?
Because the anti-racist conservative would be in the political mainstream whereas the other one wouldn't.