Primary elections or caucuses are the way that final candidates are put on the election ballot for the "big" election in November (2020 in this case). Iowa is a caucus state so those who are involved are very close to the populace in their district--they are representatives of sorts--and as far as I know, they don't exactly fight but they discuss the merits of each candidate and come to a consensus as to who will be put forward from the state of Iowa for the convention. It's sort of complicated, I think. There are a few other states that use this process, but most states have primary elections so the electorate votes for their candidate and the one with the most votes moves on to the national election process at the convention. The political conventions then hash out the final election platform and do a final count of the convention representatives who are supporting a candidate. Of course, by the time of the convention, it's pretty clear who will be selected.
My opinion is that it's not a terribly efficient system and it's fraught with problems. I've seen some surprises through the years, but I don't think it's the fairest way to do things always. The political party wields a great deal of power, so the party machine often chooses their favorite and pushes that one over others no matter what representatives might say. I think that happened in the 2016 election when Clinton was the candidate. She had been chosen long before the primaries were even done and a candidate like Sanders really was shunned by the party because they thought he was a wild card and wouldn't kowtow to party politics. Already, we see that sort of thing with the group of those seeking the democratic nomination. Biden has been promoted heavily as being the leader and many think the foregone choice, but Warren is moving up and even ahead in some areas. Sanders is down to third in the polls. I hope that the younger people are really paying attention and will vote for either Warren or Sanders to send a message that they don't want the status quo.
