Candidates in a primary election are seeking to secure the nomination of a certain political party so as to allow that candidate to run in the general election ballot. After candidates file to run in the primary election, voters select a single candidate for each office to represent their party.
As of September 2015, 17 major candidates have filed to seek the nomination of the Republican Party for the 2016 presidential election. These candidates will compete in a series of primary elections in each state, beginning Feb. 1, 2016. As the primary process continues and more states hold their elections, the number of candidates seeking the party nomination shrinks as poorly performing candidates drop out.