What change did the direct primary bring to the nominating process?

The direct primary significantly transformed the way candidates are nominated for public office by shifting the power of candidate selection from party leaders or insiders directly to the general electorate. This process allows voters to participate in the selection of their party's candidates through a primary election, where they can cast their votes for the candidates they prefer based on public support rather than through backroom deals made by party officials or bosses. The increased involvement of the public in the nominating process is a pivotal development in creating more democratic and representative systems of candidate selection within political parties.

The other options, while related to the nominating process, do not accurately reflect the impact of the direct primary. For instance, the role of party bosses was diminished rather than reinforced, and secret ballots are associated with reducing voter intimidation rather than being a product of the direct primary system itself. Additionally, the direct primary does not limit candidate options strictly to party members; it opens the process to a broader electorate, allowing a more diverse group of candidates to emerge.