Romney and Ryan are the first non-Protestant combination Presidential and Vice-Presidential ticket in the history of American elections. America has been characteristically a Baptist/Protestant country, much of which stems from what was left in Europe. This flies in the face of a national history-long trend. I actually don't think that President Obama and Vice President Biden are Protestant and Catholic, but some kind of quasi-humanism/religious liberalism, but the President claims to be Protestant.
Both Romney and Ryan come from a top-down hierarchical religious structure that belies their states rights, power to the people, economic freedom paradigm. In modern colloquial terms, what's up with that? Why are we so sure now that the Mormon president or the Pope won't be telling our candidates what to do, say in the vein of that for what John F. Kennedy had to answer for in the 1960 presidential election? I've been thinking about this recently and let me give you my take. I think I'm right, but I'm open to your thoughts.
I believe there are two parts to my answer. The first relates to the nature of Mormonism and Catholicism. The other deals with the actual system of belief of Romney and Ryan.
The Nature of Mormonism and Catholicism
Mormonism and Catholicism are morphing religions. A good example is the revelation of monogamy from polygamy shortly after the Supreme Court ruled polygamy illegal. These are not people of the book. When you talk to a Mormon, he's not convinced because of superior evidence in his written authority---that's a net minus for a Mormon. He depends on his burning in the bosom for final approval. And then things keep changing. When I talk to Mormons, they nearly unanimously desire acceptance as a main-stream Christian, even if their doctrine clashes dramatically with historic Christianity. Their acceptance seems to be bigger than their doctrine.
Catholicism reads similar to Mormonism, except longer and smaller. Catholicism has changed over the centuries incrementally. Catholicism can change the religion on a dime when the pope speaks ex cathedra. I can count on less than two hands (out of thousands and thousands) how many Catholics I've met who agree with everything in the church. They're very eclectic in their acceptance of their own doctrine. You can see by how Catholics vote that they aren't a homogeneous group.
These aren't your mother's Mormonism and Catholicism. These groups have changed to something more mainstream. They don't pose any difficulty to a Romney and Ryan view of government any more.
Mormonism matches up well with a type of Americanism. In Mormonism, Jesus takes a special trip to America, so God has some special plan for America in the religion. With Mormonism, America got Joseph Smith and Brigham Young and Utah and Salt Lake City ("Zion"), so God was really placing a special emphasis on America that fits nicely with the American exceptionalism of Romney. It might seem strange that Romney is hobnobbing with Netanyahu of Israel, but those represent the two places where Jesus visited,.
The Actual System of Belief of Romney and Ryan
I think that Romney and especially Ryan have superimposed their religious beliefs with another system of Americanism. There are a couple of books written on Americanism, one by Ayn Rand. Ryan has both espoused Rand as the one who had the greatest influence on his economics and rejected Rand's objectivism as an atheistic philosophy. Americanism, especially as Romney and Ryan are concerned, is more than objectivism. Ryan talks a lot about the individual rights given by God. This clashes with historical Roman Catholicism and is more in tune with Baptists (soul liberty) and Protestantism (Luther's individualism). Ryan's system combines Rand's objectivism and his Roman Catholic belief in God that has its home in his Americanism.
Some have written about Ryan's being the first "generation X" candidate. He represents the concerns of those who stocked shelves after graduating from college without a job and with no guarantee or even hope of receiving the benefits of Social Security to which they are paying. Romney's choice of Ryan instantly elevated his standing with generation X. Ryan feels their pain. In one sense, he's their candidate. What I'm saying here is that part of Ryan's objectivism is his generation X realism. The facts show that generation won't get anything when they are done paying into the system. Many refuse to accept the dreamy hope and change they're being sold, despite its political correctness.
The worldviews of Romney and Ryan overlap enough for them to work together. Their views find much more common ground with most Christians than Obama's and Biden's. Their principles mirror far more of the Bible than that of their counterparts.
Romney and Ryan both have a God. He isn't the historic Christian God, but they both believe he's at least the god of America, and they believe in America and what it means and what they think it has stood for. There is no way that belief will sustain this country, but many believe that it is superior to an anti-American belief that sees fairness and hope in the decline and demise of the United States.