Which method allowed voters to choose a slate of presidential electors in their state?

The method that allowed voters to choose a slate of presidential electors in their state is the popular election of president. This process involves citizens casting their votes directly for a slate of electors pledged to vote for a specific presidential candidate.

Historically, this shift to a popular vote mechanism helped promote the idea of increased democratic participation, as it enabled voters to have a direct say in the selection of electors rather than relying solely on state legislatures or other appointed bodies. As a result, it reflects the growing emphasis on popular sovereignty during the 19th century, aligning with democratic principles that became more widely accepted during this period.

In contrast, the caucus system involved party leaders meeting and deciding on candidates behind closed doors, which limited public participation. Direct election in the context of presidential elections specifically refers to voters electing their representatives or officials directly, but in the case of presidential elections, the electors chosen through the popular vote ultimately cast their votes for the president. The term "electoral selection" is not a commonly recognized mechanism within the same framework and does not accurately describe the process of how electors are chosen by voters in a presidential election.