Selecting the Nominees

Political parties use primaries and caucuses to choose presidential nominees in the United States.

Americans vote for a new president every four years. The U.S. Constitution’s requirements to run for president are relatively simple: An individual must be at least 35 years old, a natural-born citizen, and a U.S. resident for at least 14 years. But to stand out in a sea of possibilities, one of the main differentiators for candidates would be the political party they are affiliated with.

Unlike many other countries, there are only two major political parties in the United States: the Republican Party and the Democratic Party. Although there are other parties, like the Green Party of the United States and the Libertarian Party, these receive so few votes that they have little sway in national politics. 

The race to become the president of the United States is a years-long process involving campaigning, advertising, debating, nomination and election. But one of the most crucial steps along the way is the primary election and caucus process.

Primaries and caucuses are organized in each state and territory for citizens to select their preferred nominee in advance of a general election. Some states only hold primary elections, some hold caucuses and others use a combination of both. While the procedures may differ, primaries and caucuses are held between January and June, prior to the general election in November. Primaries and caucuses differ mainly in how they are funded and operated. State governments typically run primaries, which allows them to set the parameters for factors like who can participate. For example, some states have closed primary contests that only allow registered party members to vote; some follow the open primary model, which allows unaffiliated voters to participate as well. Caucuses are meetings between registered party members, run by the political parties themselves. 

The caucus system started in the early years of America’s political system, in the late 18th century, and has been used in various forms to address a range of political topics. In Iowa, for instance, caucuses not only allow activists and voters to make a case for their preferred candidate, but also to talk about issues that could be incorporated into the state party platform, said Dennis Goldford, a political science professor with Drake University in Iowa, in an interview to PBS.

The caucus system began to be replaced by the primary system at the beginning of the 20th century, with only a few states continuing with caucuses in 2020. 

At primary elections, which are similar in format to general elections, voters either fill out secret ballots in polling places or vote by mail for the candidates they believe will best represent them. Some states hold “open” primaries, which means voters can select candidates from any of the available options, regardless of the party to which they are registered. But in states with “closed” primaries, voters can only select candidates from their own parties. Variations on the open or closed primary processes—semi-open and semi-closed—also exist.

While primary elections are run by state and local governments, caucuses are private events that are directly run by the political parties.

Under the in-person caucus model, groups of voters convene by party, in places like churches and gymnasiums, to discuss, debate and lobby for their candidate of choice before voting. This can take place in the form of a secret ballot or even by voters standing together in groups for a particular candidate, then lobbying others to join them.

In each caucus state, Republicans and Democrats set their own rules, which can vary greatly. In Iowa, for example, the Republican party’s procedure involves registered Republicans gathering on a weeknight at more than 1,000 locations, writing down and submitting their preferred candidate, as well as choosing delegates to send to county conventions. Under the Democratic Party’s procedure, registered party members convene at about the same number of precincts, where they are asked to form groups based on their preferred candidates. Undecided members can also form a group. The number of members in each group is then counted, and typically candidates that receive at least 15 percent of the head count are considered “viable” or eligible to receive delegates. Then there is a 15-minute period, where attendees are given a chance to “realign,” during which members can try to convince others to join their group. According to this year’s rules, only members of nonviable groups can realign; they can either join an already viable group, or come together to help a nonviable candidate reach the 15 percent threshold. All the candidates who meet the 15 percent cutoff will be awarded delegates based on a formula put together by the Iowa Democratic Party. These delegates will go on to county conventions throughout the state. Later, at Iowa’s state-wide conventions, delegates for the Democratic and Republican national conventions are chosen. Both the Democratic and Republican caucuses in Nevada operate in ways similar to Iowa.

Caucuses generally have lower turnout than primary elections and tend to favor candidates with the most vocal and engaged backers. Caucuses also pose an access issue for many. Because they require participants to share their vote in public, are held at set times and locations, and can sometimes last for several hours, voters might not be inclined to participate. To that end, states like Washington, Minnesota and Colorado have switched from a caucus model to a presidential nomination primary model for 2020. 

Until the mid 1900’s, American citizens did not vote for their presidential nominees. Instead, they were selected by delegates at national party conventions in the summer prior to the general presidential election. These conventions still occur, but they are largely symbolic when compared to their prior role. At the convention, along with selecting their nominees for the president, the parties adopt a set of principles and goals, known as the platform. The presidential nominees also select their running mate for vice president, and the general election process begins.


Candice Yacono is a magazine and newspaper writer based in southern California.