The party members whose votes at the National Convention officially determine the two parties' presidential candidates.

Most of the delegates at the convention are obliged to vote for a candidate according to the result of primaries or caucuses in their home state. They are referred to as "pledged" or "elected" delegates.

Some delegates, however, are "unpledged" and are able to vote for any candidate at the convention. In the Democratic Party, unpledged delegates are called "super-delegates".