What is a Quarter Baby

My girlfriend and I were laying in bed watching "The Shield" the other day A gritty cop drama, awesome show by the way. One of the cops (Vick Macky) Referred to his captain as a "Quarter Baby, or maybe it was quota baby), I have never heard this term used before, anyone know what it means? It either has something to do with his being mexican, in order to get affirmative action captain position, or might be some sort of racial slure all together? Anyone know?