More than just Utah and possibly more than just cultists.
An very possible ulterior motive for Mormons who openly or secretly support the Open-Border agenda is obviously suggested by: 1) Mormon history and 2) The distribution of the Mormon population in the US.
1) Their history includes a mass exodus exodus from the US to settlements in colonies in Mexico, when statehood required them to outlaw bigamy. Mitt Romney's father (Governor George Romney) was born in such a colony in Mexico. Most only returned decades latter when a Mexican revolution made conditions too dangerous.
2) A map of the Mormon Corridor sidling up to the Mexican border raises questions of the Mormon Church's long term policy intentions regarding separate arrangements with Mexico.
Interesting map. If Roman Catholics or even two major Protestant denominations (say Baptists and Lutherans) voted like Mormons, the far left would be relegated to the lunatic fringe where they belong.