Joseph Fielding Smith writes that Joseph was inspired to predict Constitution will one day hang by a thread and the Saints will protect it.
Joseph F. Smith, Conference Report (October 1912): 10
Now, these are the commandments of God, the principles contained in these commandments of the great Eternal are the principles that underly the Constitution of our country and all just laws. Joseph Smith, the prophet, was inspired to affirm and ratify this truth, and he further predicted that the time would come, when the Constitution of our country would hang as it were by a thread, and that the Latter-day Saints above all other people in the world would come to the rescue of that great and glorious palladium of our liberty. We cannot brook the thought of it being torn into shreds, or destroyed, or trampled under foot and ignored by men.