SHORT ANSWER: These are Harold B. Lee's words based on John Taylor's
extrapolation of Brigham Young's and Orson Hyde's expression of an idea
originating with Joseph Smith.
LONG ANSWER: Joseph Smith gave a talk on 19 July 1840. The only known journal
account of this speech was made by Martha Jane Knowlton. Her journal did
not surface publicly until the 1970's. She records The Prophet saying,
"Even this nation will be on the very verge of crumbling to pieces and tumbling
to the ground; and when the Constitution is upon the brink of ruin, this
people will be the staff upon which the nation shall lean; and they shall
bear the constitution away from the very verge of destruction. " [spelling
and punctuation modernized] (Dean C. Jessee, "The Historian's Corner" BYU
Studies Vol. 19, No. 3, Spring 1979, p. 392)
Until the 1970's the only published accounts of the speech were given by
Brigham Young and Orson Hyde, 14 and 18 years after the fact, respectively.
"Will the Constitution be destroyed? No; it will be held inviolate by this
people; and, as Joseph Smith said, 'The time will come when the destiny of
the nation will hang upon a single thread. At that critical juncture, this
people will step forth and save it from the threatened destruction.' It will
be so." (JD 7:15, Brigham Young, 4 July 1954)
"It is said that brother Joseph in his lifetime declared that the Elders
of this Church should step forth at a particular time when the Constitution
should be in danger, and rescue it, and save it. This may be so; but I do
not recollect that he said exactly so. I believe he said something like
this--'that the time would come when the Constitution and the country would
be in danger of an overthrow; 'and said he, 'If the Constitution be saved
at all, it will be the Elders of this Church.' I believe this is about
the language, as nearly as I can recollect it." (JD 6:152, Orson
Hyde, 3 January 1858)
Joseph Smith also gave a speech on 6 May 1843 to the Navuoo Legion. Three
contemporary accounts of this speech (Willard Richards, Levi Richards, and
the Navuoo Neighbor ) do not record Joseph saying anything about
the constitution, but an unpublished account written many years later by
James Burgess claims Joseph to have said:
"Also upon the constitution and government of the United States stating that
the time would come when the Constitution and Government would hang by a
brittle thread and would be ready to fall into other hands but this people
the Latter day Saints will step forth and save it." (James Burgess
Notebook, Church Archives, as cited in Andrew Ehat and Lyndon Cook (1980)
The Words of Joseph Smith . SLC, Utah: Bookcraft.)
Publicly, Brigham Young gives us the 'hang by a thread' phrase. It is not
clear to me whether Brigham's public statement was based on Burgess's private
account, or if Burgess's private account is using Brigham's language. I suspect
the latter because it seems that Burgess is remembering two different speeches
(1840 and 1843) as if they were one speech and mixing what was said.
Orson Hyde is the first to say it is the Elders--in contrast to the Mormon
People--who will save the Constitution. Moreover, Brigham Young's paraphrase
said the nation (not constitution) will hang by a thread. Some 25 years after
Brigham's public statement, John Taylor, building mostly on the Orson Hyde
account, stands the doctrine up by itself without reference to Joseph
Smith.
"When the people shall have torn to shreds the Constitution of the United
States the Elders of Israel will be found holding it up to the nations of
the earth and proclaiming liberty and equal rights to all men, and extending
the hand of fellowship to the oppressed of all nations." (JD
21:8, John Taylor, 31 August 1879)
Since John Taylor, a number of church authorities--including Joseph F. Smith,
Charles Penrose, J. Reuben Clark, and Joseph Fielding Smith--talked about
[either the constitution or the nation] [either hanging by a thread or being
torn to shreds] and [either the Saints or the Elders] saving the constitution.
The first one to use all three images (hanging thread, constitution, and
Elders) simultaneously in a single sentence was Harold B. Lee in 1952.
"It was Joseph Smith who has been quoted as having said that the time would
come when the Constitution would hang as by a thread and at that time when
it was thus in jeopardy, the elders of this Church would step forth and save
it from destruction." (Harold B. Lee, Conference Report, October
1952, p.18.)
This particular phraseology was then picked up and popularized primarily
by Ezra Taft Benson and Ernest L. Wilkinson during the 1960s. Since the 1960s,
this phraseology has been repeated by numerous church authorities in a variety
of publications.