Ezra Taft Benson teaches that Joseph Smith predicted the Constitution would hang by a thread and be saved by the Saints.
Ezra Taft Benson, Teachings of Ezra Taft Benson (Salt Lake City: Deseret Book, 1988), 619
Joseph Smith predicted that the time would come when the Constitution would hang, as it were, by a thread, and at that time "this people will step forth and save if from the threatened destruction" (Journal of Discourses, 7:15). It is my conviction that the elders of Israel, widely spread over the nation, will at that crucial time successfully rally the righteous of our country and provide the necessary balance of strength to save the institution of constitutional government. If the Gentiles on this land reject the word of God and conspire to overthrow liberty and the Constitution, their doom is fixed, and they "shall be cut off from among my people who are of the covenant" (1 Nephi 14:6; 3 Nephi 21:11, 14, 21; D&C 84:114-15, 117), (God, Family, Country, p. 345.)