How are the republican and democratic presidential candidates chosen? they are nominated by their state governments. each is nominated by his or her respective party. each is chosen by the governor of his or her home state. they are chosen by the house of representatives.

The Republican and Democratic presidential candidates are nominated by their respective party. There are debates, and events held nationally by the Republican and Democratic parties in order to determine who will run for president from their party. There is a culminating election that is called a primary to decide on the candidate that will be selected from the party to run in which members of that party are able to vote for the candidate that they would like to run for president. 

Iwould say the answer would be b