[James]

They were talking on the radio about how the Iowa caucuses primary tonight works. It sounded quite quaint.

The Iowa caucuses operate very differently from the primary election used by most other states (see U.S. presidential primary). The caucuses are generally defined as "gatherings of neighbors". Rather than going to polls and casting ballots, Iowans gather at a set location in each of Iowa's 1,681 precincts. Typically, these meetings occur in schools, churches, public libraries, or even individuals' houses. Caucuses are held every two years, during both the presidential and midterm election seasons, but those that receive national attention are the presidential preference caucuses, held every four years. The rules of the caucus process to determine delegates to national conventions are determined by the party, and differ substantially between the Democratic and Republican Parties.....

.....Democratic Party

Each precinct divides its delegate seats among the candidates in proportion to caucus goers' votes. Participants indicate their support for a particular candidate by standing in a designated area of the caucus site (forming a preference group). An area may also be designated for undecided participants. Then, for roughly 30 minutes, participants try to convince their neighbors to support their candidates. Each preference group might informally deputize a few members to recruit supporters from the other groups and, in particular, from among those undecided. Undecided participants might visit each preference group to ask its members about their candidate.

After 30 minutes, the electioneering is temporarily halted, and the supporters for each candidate are counted. At this point, the caucus officials determine which candidates are viable. Depending on the number of county delegates to be elected, the viability threshold is 15% of attendees. For a candidate to receive any delegates from a particular precinct, he or she must have the support of at least the percentage of participants required by the viability threshold. Once viability is determined, participants have roughly another 30 minutes to realign: the supporters of inviable candidates may find a viable candidate to support, join together with supporters of another inviable candidate to secure a delegate for one of the two, or abstain. This realignment is a crucial distinction of caucuses in that (unlike in a primary) a voter's second choice can help a candidate.

When the voting is closed, a final head count is conducted, and each precinct apportions delegates to the county convention. These numbers are reported to the state party, which counts the total number of delegates for each candidate and reports the results to the media. Most of the participants go home, leaving a few to finish the business of the caucus: each preference group elects its delegates, and then the groups reconvene to elect local party officers and discuss the platform. The delegates chosen by the precinct then go to a later caucus, the county convention, to choose delegates to the district convention and state convention. Most of the delegates to the Democratic National Convention are selected at the district convention, with the remaining ones selected at the state convention. Delegates to each level of convention are initially bound to support their chosen candidate but can later switch in a process very similar to what occurs at the precinct level; however, as major shifts in delegate support are rare, the media declares the candidate with the most delegates on the precinct caucus night the winner, and relatively little attention is paid to the later caucuses.....

https://en.m.wikipedia.org/wiki/Iowa_caucuses

So no secret ballot, and anyone that can't attend during the hour-long process can't vote.