This was the universal belief of the entire church:


Joseph Fielding Smith wrote:The Present Status of the Lamanites
Question: "The question I have is concerning the present status of the Lamanites. I know that Laman and Lemuel and their families were cursed, but to what extent is this curse carried today? Was the darker skin all or just part of the curse? Will this curse be completely forgotten and taken away by the Lord on the basis of repentance and complete acceptance of the gospel?"
Answer: The dark skin was placed upon the Lamanites so that they could be distinguished from the Nephites and to keep the two peoples from mixing. The dark skin was the sign of the curse. The curse was the withdrawal of the Spirit of the Lord and the Lamanites becoming a "loathsome and filthy people, full of idleness and all manner of abominations." The Lord commanded the Nephites not to intermarry with them, for if they did they would partake of the curse.
At the time of the Savior's visit to the Nephites all of the people became united, and the curse and the dark skin which was its sign were removed. The two peoples became one and lived in full harmony and peace for about two hundred years.
There were no robbers, nor murderers, neither were there Lamanites, nor any manner of -ites; but they were in one, the children of Christ, and heirs to the kingdom of God.
EVIL BROUGHT RETURN OF DARK SKIN
After the people again forgot the Lord and dissensions arose, some of them took upon themselves the name Lamanites and the dark skin returned. When the Lamanites fully repent and sincerely receive the gospel, the Lord has promised to remove the dark skin. The Lord declared by revelation that, "before the great day of the Lord shall come, Jacob shall flourish in the wilderness, and the Lamanites shall blossom as the rose."
The dark skin of those who have come into the Church is no longer to be considered a sign of the curse. Many of these converts are delightsome and have the Spirit of the Lord. Perhaps there are some Lamanites today who are losing the dark pigment. Many of the members of the Church among the Catawba Indians of the South could readily pass as of the white race; also in other parts of the South.