Final answer:
The methods used by states to choose delegates for party national conventions are the open primary, where any registered voter can participate, and the caucus, a local gathering where party members openly discuss and vote for candidates.
Step-by-step explanation:
Nominees for the presidency of the two major parties are chosen by delegates at national conventions, and the methods used by states to choose these delegates include the open primary and the caucus.
Open Primary:
An open primary is a type of primary election in which voters are not required to declare party membership to vote for their preferred presidential candidate. This method allows any registered voter to participate in the selection process, regardless of their declared party affiliation.
Caucus:
A caucus is a local gathering of party members who discuss and advocate for candidates before casting their vote. It's a more public and informal method compared to a primary, where participants openly debate the merits of each candidate and select delegates aligned with their preferred candidate who will represent their decision at the party's state or national nominating convention.