What were the ideological differences between the Whig and Democratic Parties?
The Whigs mainly represented the interests of the East coast commercial and banking elite as well as the growing urban middle classes. In that sense, they inherited the mantle of the Federalist Party, the party of John Adams and Alexander Hamilton. The Whigs were unashamed modernizers who believed that the future of the United States was as a leading industrial economy. To that end, they supported measures to stimulate manufacturing such as protective tariffs and the ready availability of cheap credit through a federal banking system.
The Democratic Party, on the other hand, tended to represent the interests of small farmers and the urban poor. Democrats were intensely suspicious of the very idea of a federal banking system as they believed it would involve the concentration of too much power—both political and economic—at the center. To the likes of President Jackson, a federal banking system represented an attack on state sovereignty as well as the economic well-being of the small farmers who formed the backbone of the Democratic Party's support.
The Democrats' ideological commitment to states' rights and agricultural interests entailed a full endorsement of slavery. Although not all Whigs were hostile to slavery, a sizable proportion were, especially in New England. And many of these Whigs broke off from the Party when it nominated the slave-owning Zachary Taylor for President in 1848.
The Whig Party was formed largely in opposition to the policies of President Andrew Jackson, specifically his veto of the National Bank in 1832. Led by Henry Clay, the Whigs came to represent those people who advocated for the business interests that were emerging from the Market Revolution. They supported a number of policies, including internal improvements, protective tariffs (except for many Southern Whigs), and strong currency. Also, very generally speaking, they tended to favor national interests over sectional interests, so many of the more moderate Southern politicians were Whigs. On the other hand, John C. Calhoun, ardent sectionalist, was at one point a Whig. At least in rhetoric, the Whigs opposed a strong executive, a legacy of their origins as an opposition party to Jackson.
The Democrats tended to appeal to small farmers, up-and-coming planters in the Southwest, as well as Irish immigrant communities in the Northeast, especially New York City. Their politics emphasized expansion (which most Whigs favored as well,) tended to be proslavery, and were suspicious of government activities such as tariffs and internal improvements. Overall, the two parties were very porous, and as time went on, party division gave way to sectional division. Ultimately, the Whig Party collapsed in the wake of the Kansas-Nebraska Act of 1854.