Sidney Rigdon, who was involved with the production of the Book of Mormon, was an apostate Baptist minister who wandered into Campbellism. Campbellism is the precursor of Mormonism, and believe that one doesn't meet "the blood" until they are "under the water." They also teach that one must be baptized by someone who believes in baptismal regeneration. This heresy was promoted by Alexander Campbell, and exists today in the Churches of Christ, the Disciples of Christ and "the Christian Church," the latter being the designation of a moderate Campbellite branch.
Interestingly, Alexander Campbell took one look at the Book of Mormon and immediately recognized it as the fake it is. Here is Campbell's take on the Book of Mormon, a fake inside and out:
http://www.lds-mormon.com/campbell.shtml