Which president's election marked the beginning of the modern Democratic Party?

The election of Andrew Jackson in 1828 is widely recognized as the event that marked the beginning of the modern Democratic Party. Jackson's presidency is significant for its populist approach and the emphasis on the "common man" in politics, moving away from the elitist politics of earlier periods. His campaign strategy involved a strong sense of grassroots mobilization and voter engagement, which became central to the Democratic Party's identity.

Jackson's victory also represented a shift in political power dynamics, as it solidified the Democratic-Republican Party's evolution into the Democratic Party that we recognize today. Under his influence, the party adopted platform policies that emphasized agrarian interests, expansion, and populism, distinguishing itself from the Federalists and other earlier political factions.

In contrast, while the other figures listed played significant roles in U.S. history—Jefferson in promoting democratic principles and individual liberties, Lincoln in preserving the Union during the Civil War, and Roosevelt in modernizing the role of government—the fundamental transformation and establishment of the Democratic Party as a major political force is most closely associated with Jackson's election.