Rick Santorum writes:

In a recent attempt to defend Kennedy, Democratic U.S. Rep. Patrick Murphy of Bucks County said, “We don’t legislate at the orders of the Vatican; we legislate what is in our conscience and what we think is good for our country.”
I agree. But in 16 years as a Catholic in public office, I never received an order from the Vatican or any clergyman.
I also agree with Murphy – as does the catechism – that Catholics must be true to their consciences. But that is not a free-floating guide that we can define ourselves. A Catholic is required to form his conscience in accordance with the church’s teachings on faith and reason, and to act in a morally coherent and consistent way, both privately and publicly.
Finally, the church maintains that there is a natural law that forms the basic moral foundation of society and that can be known through the exercise of reason. Thus, a Catholic public official with a well-formed conscience can arrive at correct moral conclusions not by faith, but by reason.