Presidential primaries work much like primary elections for other federal or state offices. Eligible voters cast ballots either in-person or absentee to select the party’s nominee. Some states used closed primaries in which only voters registered to that political party can participate, while others allow voters of any political affiliation to participate.
Caucuses, on the other hand, are intended as gatherings for the politically active, and require at least an hour (or more) for participants to spend selecting their choices - unlike voting in a primary which takes a matter of minutes. Caucuses vary state-by-state and depending upon which party is running it. For example, Iowa Democrats vote with their feet, but Republicans use a secret, informal ballot.
When delegates are allocated proportionally (the policy for all Democratic primaries and caucuses and some Republican primaries and caucuses), there is usually a minimum threshold of votes required to receive any delegates. The more crowded the field, the more likely it is that some candidates will receive fewer votes than the minimum required, which means their supporters’ votes are essentially wasted.
In the winner-take-all-style (or winner-take-most) that some states’ Republican parties use, the ‘majority’ needed to win all that state’s delegates can be much lower than 50 percent of vote.
Both styles fail to reflect the full nuances of party voters’ choices and viewpoints,setting the stage for an unrepresentative nominee.