Many people here are political junkies, so may already know much of what I’m going to say. However, I thought it might be beneficial to remember how Iowa caucuses work at the ground level. Attempts to allow people to participate remotely were called off due to security concerns, so participants will need to be physically present at a certain location at 7pm local time when doors are closed. This means that participants will continue to skew older (no younger children to worry about) and richer (no part time/third job work) than the Iowa population in general. Support must be stated publicly, meaning that social demands are often overlooked in planning and reporting. I know of sororities, for example, that threaten to kick out any “sister” who does not caucus for their chosen candidate. Employers and children at home also receive such pressures.
How it’s reported: In addition to the stupid “expectations” game, Iowa is generally reported on the basis of who won how many delegates. This can be very different than which candidate had the most supporters. As with our country in general, smaller, rural precincts often have a caucusgoer:delegate ratio smaller than urban precincts. The system privileges dirt over people. There will be an “entrance poll” reported at 7 local time, but that’s often filler until results emerge.
How delegates are awarded: Each precinct has a certain total of delegates at stake, usually 4-8. Candidates win delegates proportional to how many caucusgoers in a certain precinct support them – with one important caveat. And that is, a candidate must have 15% of committed supporters to be “viable”. So if Buttegieg has 14 supporters out of the 100 who show up, they must either convince someone else to join them, or they are non-viable and have the chance to go somewhere else. There is also an “uncommitted” option. Some caucusgoers are so invested in their candidate they are immovable. Others can be moved, especially if campaigns make a deal (like the notorious agreement to share delegates between Kucinich and Edwards in 2008).
Being a second choice for candidates can be important. Looking at Iowa polling, one can expect Biden and Sanders to be viable nearly everywhere, and Warren in many places, though it is important to note how easily influenced and prone to changing their minds Iowa voters are. That said, there will be many, many caucuses where the margins are determined where supporters of non-viable candidates go. Supporters of candidates such as Booker, Steyer, or Yang may arrive having reconciled themselves to having to go to a second-choice, but a large number of caucusgoers decide on the spot.
How this matters in the long term: In terms of momentum and media coverage, this matters a lot. In terms of the selection of delegates to the national convention…very little. See, when it is determined that Biden will get, say, 2 delegates, those people are selected right there. Those 2 delegates have no formal binding to keep their word when they arrive at the county convention weeks later, where the whole exercise is repeated to select delegates to the state convention, then from their to the national stage. Iowa is rife with delegates pledged to one candidate flipping to another at the county or state level. If there is a brokered convention, this sort of thing might matter.
A final note: Often, successful campaigns have a strategy on caucus day about who to target among non-viable candidates, and how to get people of their choices into those delegates spots. As Dean learned in 2004, having locals who are strong supporters is essential in this process.