The hockey hunk, who planned to wed high school sweetheart Bristol Palin, said in a first-person article for the October issue of Vanity Fairthat the former veep candidate wanted to keep her teen daughter's pregnancy a secret and adopt the baby herself.
"Sarah told me she had a great idea: we would keep it a secret -- nobody would know that Bristol was pregnant. She told me that once Bristol had the baby she and (husband) Todd would adopt him. ... I think Sarah wanted to make Bristol look good, and she didn't want people to know that her 17-year-old daughter was going to have a kid."
Johnston claims in the article that Palin became consumed with greed once she lost the presidential election and about two weeks after she returned to Alaska began talking about ways to earn "triple the money" by writing a book or doing a show.
Get more: Vanity Fair