The article focuses on the history of the Democratic Party during the bipartisan Democrat-Whig system. It shows how the nationwide issues of tariffs, slavery and expansion influenced the formation of sectional factions. Having progressed from a small-scale factional struggle, by the end of the period under review the party consisted of two major factions divided geographically by North-South. Particular attention is paid to the “Young America” movement, which originated with young and ambitious politicians who promoted infrastructure development and the idea of expanding borders. This idea came to be known as the "idea of predestination". Although the movement died out in the 1840s, the Predestination idea became the ideological basis for the invasion of Texas, California and other Mexican territories, as well as for the justifcation of the spread of slavery. The article examines how the controversy over the extension of slavery to the newly acquired territories caused a division of political forces in the country. "The Wilmot Proviso", which prohibited slavery in these territories, provoked protests from southern politicians, who not only began voting against the amendment in a single section, but began preparations for a convention that would decide the Southern states' secession from the United States.