All you want to know about selecting a Presidential nominee
Graeme Edgeler at Public Address has blogged at length on how the US primary and caucuses work on selecting a presidential nominee for both party. It’s very comprehensive and a great read.
Incidentally while winning the Iowa caucus is obviously very desirable for the candidates, it is by no means a lock for the nomination. Far from it.
In 1992 Bill Clinton only got 3% in Iowa but went on to win the nomination. In 1988 the nominee Michael Dukakis got 22% and was 3rd
For the Republicans in 1988 Bob Dole beat VP (and nominee) George HW Bush by 37% to 19%. Pat Robertson got 25%.
And ironically in 1980 George HW Bush beat Ronald Reagan by 32% to 30%.
Nevertheless almost the entire political world is focused on Iowa today to get their first hint of who might be the future Commander-in-Chief.