GQC maintains that plural marriage only necessary in one's heart for exaltation.
"Remarks made by Prest. George Q. Cannon," Deseret News, November 14, 1891, 4
Now, brethren and sisters, I know there are a great many people who feel that, this being a principle of exaltation, they may be in danger of losing their exaltation, because of their inability to obey this. I want to say to all such that the Lord judges our hearts; He looks at our motives. There, were a great many men in past times who never had the privilege of obeying this doctrine, because the law was not given to them. Do you think that they are excluded from exaltation? Do you think that they will be deprived of celestial glory? I do not. Eternity is a long period, and we cannot conceive of its duration. The Nephites, according to all that has come down to us, were monogamists. This law was not given to them, as far as we have any account. Yet they were a great and mighty people before the Lord. They had Prophets and mighty men among them.