Did JFK help or hurt the Catholic Church? He hurt it. Did Jimmy Carter and Bill Clinton help or discredit the Southern Baptist Church? They hurt it. I could go on about the Bushes and their liberal churches.
It is a patently false assumption to think that Romney will help the LDS Church. The exact opposite is more likely correct.
I don’t buy your premise that any of those people hurt their churches, that seems absurd, but none of them were powerful leaders within their church.
Romney is a Bishop and Stake president, and headed for higher places within his cult.