• Democrats vs. Whigs, 1820s-1850s
• Competing factions within the old Republican Party split into two new opposing parties during Andrew Jackson's presidency
• Jackson's faction, now known as Democrats, was rooted in the West and South and favored small national government
• Jackson's opponents, rooted in the Northeast, called themselves Whigs and favored government action to improve American society

The National Republicans, led by John Quincy Adams, Henry Clay, and Daniel Webster, believed that government power should be used to advance a wide range of social and cultural improvements. Adams proposed an elaborate program of internal improvements that included traditional projects such as roads, canals, and harbors, as well as more innovative ideas such as a national university and government support for scientific research. Other National Republicans argued that government authority should be used to advance moral reforms such as temperance and Sabbatarianism. This faction of National Republicans, soon to become a full-fledged party known as the Whigs, maintained something of the Federalists' earlier confidence in the benefits of an active national government. In fact, the Whigs drew most of their support from the northeast, just as the Federalists had in earlier decades. But there was a more middle-class orientation to the Whig agenda. It was less narrowly focused on economics on a grand scale and more focused on using government power to improve and "moralize" the quality of life in America's communities. For example, Whigs believed that public institutions like schools, hospitals, and asylums could elevate the character and improve the health of the public.

The Democratic Republicans, led by Andrew Jackson, insisted that they were the true heirs of the Jeffersonian Republican tradition—but to emphasize their commitment to advancing the interests of the common man, they soon simplified their name to Democrats. These Democrats favored a smaller national government and opposed, in particular, any Whig proposal that seemed to threaten their economic, social, or cultural freedoms. They viewed the Whigs as self-righteous meddlers, and they argued that, historically, federal intervention in the economy served only a small economic elite. Democrats did, however, encourage forcible government removal of Native Americans in order to open western lands to white migrants. And Democrats did support war with Mexico in the 1840s in order to expand the western domain.

The Democrats controlled the presidency during most of this second party era and succeeded in advancing most of their major policy ambitions. Ninety-thousand Indians were moved out of the eastern states, the national boundaries dramatically expanded through war with Mexico, the institutional centerpiece of the Federalist era—the Bank of the United States—was destroyed, and America's public lands were made more accessible to common farmers. But during the 1850s, the issue of slavery shattered the existing political alignments and led to the emergence of a third era in American political history.