which level of part organization is most responsible for helping the party’s nominee win the presidency?

The level of party organization that is most responsible for helping the party’s nominee win the presidency is the national level. This includes the national party committees, such as the Democratic National Committee (DNC) or the Republican National Committee (RNC), which coordinate campaign strategies, fundraising, and support for the nominee at the national level. While precinct, county, and state organizations play important roles in local and state elections and grassroots mobilization, the national party organization has the broader scope and resources dedicated to the presidential campaign.