Mosiah apparently sends emissaries out to know the will of the people for their next king.
This is a problematic passage, because it does not fit the typical pattern of transfer of power from king to king. This is prior to the establishment of the judges, so it really is not an elected king. Indeed, verse 6 suggests that the voice of the people simply confirmed the typical right of kingship.
A possible parallel to this situation occurs in the city of Lehi-Nephi when Limhi and his people are planning an escape:
Mosiah 22:1
1 And now it came to pass that Ammon and king Limhi began to consult with the people how they should deliver themselves out of bondage; and even they did cause that all the people should gather themselves together; and this they did that they might have the voice of the people concerning the matter.
It is possible that Nephite society maintained some form of communal involvement even with a monarchy. Such communal involvement would not be out of place in a Mesoamerican context, though our firm information for such social interaction must forcibly come from a much later period that the Book of Mormon. Nevertheless, it is interesting that such connection to the voice of the people from a powerful ruler was not a foreign conception.
Jacques Soustelle describes the head of a political/kin organization among the Aztecs of Tenochtitlan:
“Each district or calpulli in the capital had its own chief, the calpullec…‘he never did anything without taking the opinion of the elders.” (Soustelle, Jacques. The Daily Life of the Aztecs. Stanford University Press. 1970, p. 40).
Textual: As noted in the comments on Mosiah 28:20, that verse was originally attached to this first verse of our current chapter 29. To restore the conceptual reading, let’s examine the reattached paragraph:
Mosiah 28:20
20 And now, as I said unto you, that after king Mosiah had done these things, he took the plates of brass, and all the things which he had kept, and conferred them upon Alma, who was the son of Alma; yea, all the records, and also the interpreters, and conferred them upon him, and commanded him that he should keep and preserve them, and also keep a record of the people, handing them down from one generation to another, even as they had been handed down from the time that Lehi left Jerusalem.
Mosiah 29:1
1 Now when Mosiah had done this he sent out throughout all the land, among all the people, desiring to know their will concerning who should be their king.
Mosiah 28:20 begins with “and now” which Mormon uses as a marker of new subjects. Mormon has split his story of the transfer of power from king to judges into two pieces, the preparation, and the creation of the judges. Chapter 29 will discuss the creation of the judges.
Mosiah 29:2
2 And it came to pass that the voice of the people came, saying: We are desirous that Aaron thy son should be our king and our ruler.
The polling of the people by Mosiah may not cleanly fit into typical conceptions of monarchy, but it does have a very important ramification. In this verse we find that “the voice of the people” proclaimed a desire for Aaron to be king. This phrase, “voice of the people” will become the underpinning of Mosiah’s discussion of the value of the judges (see verses 25-29).
In the context of electing judges, we certainly understand the “voice of the people.” What is important is that the mechanism appears to have existed to assess the voice of the people. In the shift from monarchy to judges, the reliance upon “the voice of the people” would be greater. If there were no accepted mechanism for assessing that voice, the transition would have been much harder. Thus whatever function it served in the monarchy, the mechanism to assess the voice of the people was apparently in place and ready to become the underpinning of the reign of the judges.