Nah, it's Romney's constant flip-flops that make me not trust him as far as I could throw him - it has nothing to do with his religion. We don't need a guy who will say anything to win a given election, and then do a 180 and say something else when trying to win a different election. Clinton was quite good at that.
For the vast majority of conservatives who oppose Romney, its not his Mormonism that turns us off. Its his unprincipled, two-faced, lying approach to politics that we oppose.