The 1860 Republican Party convention in Chicago created a platform that clearly opposed the expansion of slavery in the West and the reopening of the slave trade. However, nothing in the document claimed that the government had the power to eliminate slavery where it already existed. The American political parties, now called Democrats and Republicans, switched platform planks, ideologies, and members many times in American history. These switches were typically spurred on by major legislative changes and events, such as the Civil War in the 1860’s, and Civil Rights in the 1960’s. The Republican Party Forms around the Issue of Slavery. Slavery is quite possibly the most influential issue underlying American politics from 1776 to 1865, and the single greatest issue in the formation of the Republican party. The digital collections of the Library of Congress contain a wide variety of material associated with the presidential election of 1860, including manuscripts, broadsides, prints, political cartoons, sheet music, articles, and government documents.