During which phase do parties finalize their nominees for president?

The correct answer is that parties finalize their nominees for president during national conventions. National conventions serve as the formal event where delegates from various states gather to confirm their party's nominee for president. This process occurs after the primary elections and caucuses, where candidates compete to earn delegates based on their performance. During the national convention, delegates officially vote to select the party's candidate, typically acknowledging the candidate who has garnered the most support during the primaries. This event is significant for establishing party unity and laying out the party’s platform ahead of the general election.

In contrast, primary screenings refer to the process wherein candidates campaign across states to win delegates, not the finalization of nominees. General elections are when voters choose among the confirmed nominees from various parties, and campaign rallies are events held to garner support, but they do not play a role in the actual nomination process. The national convention is thus the critical point at which the party's choice is solidified.