The Republican Primary Caucus in Iowa is just a glorified secret ballot.
But in the Democratic Primary, you go in and stand with a group of folks who support the candidate of your choice. This year the groups will be for Clinton, Sanders, O’Malley, and Undeclared.
So each group then tries to attract or take members from other groups. Any group that comprises less than 15% of the total people present, is not considered viable, and its members must join one of the other groups.
(Attending an Iowa, or similar Caucus process, should, I think, be mandatory for students of Social Psychology.)
Depending on the number of delegates that a particular locality is assigned to allocate, the number of folks who show up for each group, and the individual political and social skills of the people who show up, the possible machinations that actually occur seem infinite, especially across all the caucuses that are occurring simultaneously.
Consider just one possible scenario: You are an O’Malley supporter. Your group is only 5% of the total people present. Undeclared is 10%. Sanders is 43%, and Clinton is 42%.
You could try to get your group, en mass, to go to Undeclared to make it a viable group. But if one person in your group, or the Undeclared group, went over to Clinton or Sanders, you might, then be left with choosing one of their groups, as would the Un-declared group. What then?
And there are as many possible basic scenarios as there are individual caucuses.