The US government did not persecute mormons, that is part of the mormonism revisionist history.
svcw, in Missouri and Illinois you are exactly right. The US Government was not involved with the persecution of the LDS people. It was local mobocracy, local and State governments who were involved. A petition was taken to the President by the LDS at the time and he responded that though he felt that their cause was just, he could not help them.
However, in the 1850s the situation was different. At that time it was a US Army that was coming to the LDS settlements around the Great Salt Lake and the quotes given on this thread by General Johnston of that Army and Colonel Smith as regards what they intended on the LDS people are accurate.
Luckily, the LDS had evacuated SLC and ultimately the impasse was resolved.
At any rate, refighting the Mormon War is a tactic of the left right now. Romney is the nominee and aiding Obama will get us nowhere.