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There were numerous people, including Mrs. Spalding and her daughter, who distinctly remember Mr. Spalding claiming that Sidney Rigdon had likely taken the manuscript. There are statements from folks in Spalding's area, or Rigdon's area, claiming that they had heard Rigdon talking about having a document, working on something, and he would sometimes pull the document out and show it to guests.

There is also evidence suggesting that Rigdon and Joseph Smith Jr., the prophet of the restoration, had met before 1831. The old view was that the Spalding-Rigdon theory was invented around the time that Eber D. Howe and Doctor Philastus Hurlbut were working on "Mormonism Unveiled," which places it at 1833 or 1834. However, a newspaper from 1831 places Rigdon and Joseph Smith in a relationship with each other, suggesting they may have met earlier.

Some believe that the Book of Mormon resembles Spalding's manuscript and therefore hypothesize that Sidney Rigdon must have taken it, copied it, or otherwise used it to create the Book of Mormon. There are also stories indicating that Rigdon may have stolen the manuscript outright.

In terms of the scriptures, Second Nephi chapter 3 in the Book of Mormon is of interest. It contains a purported prophecy of Joseph of Egypt about a "choice seer" who will be raised up from his descendants, who will also be named Joseph. This seer is to do a work of great worth, bringing knowledge of the covenants made with the fathers. The prophecy also mentions a Moses figure who will be given power and judgment but will not have a loose tongue, implying that he will have a spokesman.

This brings up questions about the relationship between Joseph Smith and Sidney Rigdon, as Rigdon seemed to have immediate co-equal billing with Smith and acted as if he was in charge. Rigdon collaborated with Smith on new scripture, such as the Book of Moses and the inspired translation of the Bible. There are also internal evidences within Mormon theology and scripture that suggest a connection between Smith and Rigdon earlier than the official 1830 meeting...