In principle, local parties in states are allowed to decide for themselves when to organize their primaries. The national organization does follow certain guidelines. For example, Iowa remains first and New Hampshire second although those states are not representative of the entire country.
Every election cycle the primary dates vary a little. This is because state parties are expected to set a date for their primary and most want theirs to be relevant to the overall contest. If you are dead last,
In 2020 that means a trip to Nevada and a week later to South Carolina. But only the Democrats go there. The Republicans who then hold an extended break until Tuesday, March 3rd. That date is important because you will know it by another name: Super Tuesday.
Republicans? Primary? That’s right, the Republican party will also hold primaries in 2020 despite Donald Trump being president and standing for election himself. The entire process from 2016 is repeated again for the Republicans. So other candidates can apply for the Republican nomination. That is the theory, but in practice the current president usually wins the primary with little difficulty.
After Nevada and South Carolina, many candidates will drop out of the race. Those who do not achieve good results after four states usually suspend their campaign. They usually run out of money because donors would rather put money on a winner than on someone who doesn’t seem to stand a chance. In addition, the final winner (if he / she becomes president) has quite a few nice jobs to hand out. If you have ambitions, it’s probably beneficial to leave the fight at a relatively early stage. Joe Biden, who became the vice president under Obama, is a good example of this.
Another tradition in the primaries is ‘Super Tuesday’. This is a day when many states collectively hold their primaries. After Super Tuesday it should be clear who the top candidates are. In 2020 Super Tuesday is March 3rd. If you know that the primaries last until well into June, then it seems strange that such an influential moment is planned so early in the primaries.
Realistically, the fight is usually over after the big states have voted. So after states like Ohio, Pennsylvania, Illinois, Florida, New York, California and Texas, a very large proportion of delegates is already divided among the candidates. Almost half of Americans live in these seven states. So the 28th of April is the last moment at which a sizeable number of delegates is up for grabs.
So the end of the primary season might be a lot sooner than you think. But don’t count out Bernie Sanders, he kept the 2016 Democratic primary going until the very end, even though there was only a marginal chance he could win.