Fate of winning candidates following Iowa and New Hampshire primaries 1972-2020

In the build up to each US presidential election, primaries and caucuses are used by the major parties to nominate their candidate for the general election. A primary election is run by the state and local governments, whereas the caucuses are private events that are organized and administered by the respective parties. Primaries involve voters going to the ballot box to decide who their respective candidates will vote for in the respective national conventions. Most states conduct "open primaries" that are open to all eligible voters; while a few states conduct "closed primaries" that are only open to party members. In contrast to this, caucuses involve party members meeting at events where they then discuss who they will vote for, although this system is gradually being phased out, with ten states switching from caucuses to primaries in 2016.

Iowa caucus

Iowa is generally the first state to select their nominees, and this is done during the Iowa caucus, which has become one of the most important and focal events on the campaign trail. While the winner is not guaranteed the party's nomination, the event helps to establish who the frontrunners in each race are, and in the past, has seen many candidates drop out of the race following poor performances. In the past fifty years, the Iowa Democratic caucus has put forward nine (out of thirteen) candidates who would go on to contest the general election (although two of these primaries were uncontested), while the Iowa Republican caucus has put forward just six (out of twelve) candidates who would receive their party's nomination (with four of these being uncontested). In recent years, many have criticized the influence afforded to the Iowa caucuses, as they do not feel the state (which is ninety percent white) reflects the diversity or demographic makeup of the United States; whereas supporters of the caucuses argue that these events prevent candidates from ignoring voters in smaller and more rural areas in favor of those in larger metropolitan areas, and requires them to conduct politics on a more personal level.

New Hampshire primary

The New Hampshire Primary usually takes place one week after the Iowa caucuses, and is the second major event in the campaign. As in Iowa, this primary's significance comes from the vast amount of media coverage afforded to it on the campaign trail, and it is often seen as a second (and final) chance for those candidates who underperformed in Iowa. Historically, the New Hampshire primary has a success rate below fifty percent when predicting the Democratic nominee (or forty percent when uncontested races are not included), while it has correctly chosen the Republican nominee on all but two occasions. As this primary is open to all voters, it is seen as a much better indication than Iowa of who will perform well in the general election (especially among undecided voters), and has allowed candidates such as John McCain in 2008 and Bill Clinton in 1992 to stage surprising comebacks in their respective races.