The democratic party is the left leaning party that is loosely held together and sees a wide range of left wing factions. They prefer globalist policies, open borders, free trade, welfare state policies, and other left leaning ideals. Democrats often prefer secularism, and are generally more accepting of civil rights movements. The closest thing you have to a dominant faction in the Democratic party, would be the Social Democrats. However, in reality, it's more of a loose coalition of leftists who often vary on where they stand on the spectrum.