The last year of his life was a stormy one. Rumors of "spiritual wifeism" split the community of Latter-day Saints.
It all culminated in June of 1844 when William Law (a former Counselor to Smith) published "The Nauvoo Expositor," on June 7th. This was the first and only edition of the paper, and in it Law exposed the practice of plural marriage in Nauvoo. He also exposed the underground teaching of multiple gods.
Smith, both mayor of Nauvoo and General of the Nauvoo Legion, ordered Law's press destroyed and thrown in the Mississippi River.