Final answer:
The rise of the national convention was significant as it expanded the presidential power base by involving the masses in the selection process and strengthened the parties' appeal while still maintaining a crucial role in the nomination process and setting strategies for general elections.
Step-by-step explanation:
The rise of the national convention was important because it C) gave the presidency a mass popular base that would eventually support and demand increased presidential power. Initially, party leaders exerted strong control over the nomination process during conventions. Over time, however, primary and caucus voting systems shifted this power to the general populace, enabling a more democratic selection process and enhancing the mass appeal of candidates. Although now primaries determine the outcome, conventions still play a significant role in shaping party platforms, strategies, and showcasing potential future leaders, like Barack Obama's rise following his 2004 convention speech.
Despite changes in media coverage and public engagement, national conventions remain pivotal for national discourse, embodying the grandeur of political parties and setting the stage for the general election. They mark a transition from primary season to the general election campaign, serving as a formal nomination event and a platform to unite the party and present its vision to the nation.