The national conventions of the political parties are the culmination of the primary election process. Once the national conventions have been held, and the candidates from the political parties have been nominated and chosen, the presidential election begins in earnest as a contest between the candidates from the political parties. Any divisions or factions that have surfaced within a political party up to the nomination process tend to be set aside and the entire party becomes unified behind its candidate and begins to work to get that person elected.
Some people choose to run for president without being affiliated with a political party.
Such independent candidates need not concern themselves with getting nominated by a party, but must meet other requirements. For example, such candidates are required to collect a large number of signatures to support their nominations. The sources of funding used by independent candidates comes from personal funds and loans as well as fundraising campaigns. An independent candidate for President must file a declaration of candidacy and a certification of the candidate's selection for vice president with the secretary of state prior to circulation of the candidate's nominating petitions. The candidate and the candidate's selection for vice president must sign the certification before it is filed.