The early Latter-day Saints felt they were building the spiritual and political kingdom of God on Earth. The concept of the kingdom included political ideals as well as economic and social. Joseph Smith ran for US president on this premise. After his death, when the Nauvoo charter was repealed, a political vacuum was created, and Brigham Young was there to fill it. As the Saints went west, ecclesiastical and political leadership was one and the same. Brigham Young was Church president and the first governor of Utah, but in 1858 the US appointed a non-Mormon governor, and the Mormon-federal conflict continued for decades. The Church explored utopian communities but in the end abandoned that system. While Brigham Young's statements on church and state relations may seem inconsistent, he was not strict in his use of political terminology. His decisions were based in theology but were made to suit what was expedient and practical.
Melville, J. Keith
"Theory and Practice of Church and State During the Brigham Young Era,"
BYU Studies Quarterly: Vol. 3
, Article 5.
Available at: http://scholarsarchive.byu.edu/byusq/vol3/iss1/5