John F. Kennedy scared the American people by simply being Catholic. People were afraid of his religion being a factor is his policies. Kennedy was not a priest or pastor or reverend. Romney was.
I have heard nothing of Romney's position is the Church of Jesus Christ of Latter Day Saints. I presume that is because people do not understand the terms. Mitt Romney was a bishop and a stake president. A bishop presides over the congregation of one church, similar to a Catholic priest. In Catholic terms, a stake president is an archbishop. He presided over a dozen or so congregations.
Why the difference?
Is it because religious tolerance is higher now than 50 years ago? No. Look at the 'Obama is Muslim' trash.
Is it because the LDS church is considered Protestant like most of the number of churches in the US? Certainly not. Look at the protests in Salt Lake every April.
It is because Democrats take the moral high road and do not bash someone's religion? Possibly, but this is not bashing. This is absolute truth. I know these things are true, because I am an LDS Democrat.