More publicly, George Q. Cannon helped promote vicarious work for the dead towards as a means for helping those without opportunities.

“Some people have supposed that the doctrine of plural marriage was a sort of superfluity, or non-essential, to the salvation or exaltation of mankind. In other words, some of the Saints have said, and believe, that a man with one wife, sealed to him by the authority of the Priesthood for time and eternity, will receive an exaltation as great and glorious, if he is faithful, as he possibly could with more than one. I want here to enter my solemn protest against this idea, for I know it is false. There is no blesssing promised except upon conditions, and no blessing can be obtained by mankind except by faithful compliance with the conditions, or law, upon which the same is promised. The marriage of one woman to a man for time and eternity by the sealing power, according to the will of God, is a fulfillment of the celestial law of marriage in part—and is good so far as it goes—and so far as a man abides these conditions of the law, he will receive his reward therefor, and this reward, or blessing, he could not obtain on any other grounds or conditions. But this is only the beginning of the law, not the whole of it. Therefore, whoever has imagined that he could obtain the fullness of the blessings pertaining to this celestial law, by complying with only a portion of its conditions, has deceived himself.” (Joseph F. Smith, 1878, JD 20:29)

Do we know whether Joseph F. Smith changed his views to be more in accord with Elder Talmage’s 1894 statement after the Manifesto?

“A man can be saved in the Celestial Kingdom with but one wife,” (Brigham Young Letterbook II:735)

I hear a good book from that idea. However, I think it would be innacurate if you don’t add Joseph Fielding Smith to that list. He was influencial long before he became Prophet.