Before the actual Presidential Election, a host of states hold another election called a primary. This part of the process is needed to figure out who will run for president in each party.
A primary election is held at the ballot box, just like other elections, and is run by state governments. 37 states use primary elections over caucuses. Primaries are held a couple of different ways, depending on the state, but all will result in a number of delegates who will go onto the national convention to select a Presidential nominee.
In “Closed” primaries… voters must declare which party they support and can vote only in that party’s primary. In “Open” primaries… registered voters from any political party can vote for candidates of either party.
And when it comes to delegates, some states go by winner-take-all. That means the presidential candidate with the most primary votes claims all that state’s delegates at each party’s national convention, ‘or huge meetings held a few months before the election itself. At the convention, the nominees are decided by delegates from each state.
Other states award delegates by proportion. For instance In a proportional primary, a candidate who won 20 percent of the vote would get 20 percent of that state’s delegates. In some states, a combination of the primary and caucus system are used.