Jacksonian democracy contributed to the mistreatment of the Indians by giving the voices of the common white people more power in American government.  The common white people were the ones who were most likely to come into competition with the Indians.  They were the ones on the frontiers, taking lands that the Indians claimed.  The elites, meanwhile, were more likely to live back in the settled areas and have no real need to mistreat the Indians.

As the common white people came to have more power, their demands were heard more by the government.  Among these demands was the demand for the Indians to be removed from lands that the whites wanted.  Jacksonian democracy made these demands more likely to be heard and, thereby, contributed to the mistreatment of the Indians.