Iwas a democrat who angered southern members of my party through my introduction and support of the idea of popular sovereignty. i stated in the freeport doctrine that territories had a legal right to keep out slavery. who am i?

The correct answer is Stephen Douglas.

Douglas was the political rival of Abraham Lincoln during the late 1850's and early 1860's. Douglas ran against Lincoln and both men became famous for their debates during the election of 1858. During this campaign against each other, Douglas developed the Freeport Doctrine during his debate with Lincoln in Freeport Illinois. In this doctrine Douglas argued that US citizens could find a way around the Dred Scott vs. Sandford decision (made by the Supreme Court) by not creating a police force to enforce the rights of slave owners.