What were the ideological differences between the Whig and Democratic Parties?
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.