By Dan Gilgoff and Dan Merica

Washington (CNN) – Mitt Romney’s selection of Wisconsin Rep. Paul Ryan as his vice presidential running mate promises to cast a spotlight on American Catholicism in an election year when the tradition has already been a major focus.

Ryan, a Catholic who chairs the House Budget Committee, is better known for his outspoken fiscal conservatism than for leading on conservative Catholic social causes like opposing abortion and gay marriage.

But Romney called attention to Ryan's religion Saturday in introducing him as his running mate: "A faithful Catholic, Paul believes in the worth and dignity of every human life," Romney said.

And socially conservative groups were quick to praise Ryan's selection, with the president of National Right to Life saying that "Ryan has a deep, abiding respect for all human life, including unborn children and their mothers, the disabled and the elderly."

Ryan’s advocacy for cutting taxes and trimming the deficit — he is the architect of the GOP’s proposed federal budget — married with his willingness to talk about fiscal belt-tightening in moral terms and his low-key social conservatism speak to a political moment in which the economic concerns of the Tea Party and the social focus of the Christian right have merged into a relatively cohesive anti-Obama movement.

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Ryan’s presence on the ticket also could increase Romney’s appeal among the millions of middle-of-the-road Catholic voters who populate key swing states, like Ohio and Pennsylvania. Catholics are considered the quintessential swing vote, and no presidential candidate has won the White House without winning Catholics since at least the early 1990s.

With Romney, a Mormon, selecting a Catholic, Obama is the only Protestant in the 2012 presidential race (Vice President Joe Biden is also Catholic).

"As a conservative Catholic, Ryan is likely to appeal to a number of Catholics in the Midwest,” said John Green, a professor of religion and politics at the University of Akron in Ohio. “Catholics who are concerned about religious liberty, he is certainly a positive there."

The Catholic Church has helped frame this year’s election by strenuously opposing a rule in President Obama’s health care law that requires insurance companies to provide free contraception coverage to nearly all American employees, including those at Catholic colleges and hospitals. The Democrats have said that Romney’s and the GOP’s support for the Church’s position constitutes a “war on women,” while Romney and his party say Obama’s rule represents a “war on religion.”

In an interview with CNN, former GOP hopeful Newt Gingrich, who is Catholic, said that Ryan would shore up support in a Catholic community that feels it is “under siege.”

Romney released an ad Thursday repeating the war on religion charge. Next week, Sandra Fluke — a Georgetown University law student who was thrust into the national spotlight after radio show host Rush Limbaugh called her a “slut” for her role in supporting Obama’s contraception rule — will introduce the president at a stop in Denver.

Ryan’s own Catholicism became a major issue this year, with the United States Conference of Catholic Bishops criticizing his proposed federal budget for what the bishops said would be its adverse impact on the poor.

The bishops cautioned against overreaching budget cuts that endanger “poor and vulnerable people.” The bishops’ message called on “Congress and the administration to protect essential help for poor families and vulnerable children and to put the poor first in budget priorities.”

This split between politically conservative and liberal Catholics has existed for decades in the Catholic Church. But with Ryan running for vice president, some experts expect this divide to be sharpened.

"What Ryan will highlight is a division within the Catholic community,” Green said. “More politically liberal Catholics are very critical of the Republican approach and the Ryan budget, but Ryan has taken them head on.”

In an April speech at Georgetown, a Catholic school, Ryan defended his budget in religious terms.

“The work I do as a Catholic holding office conforms to the social doctrine as best I can make of it,” Ryan said. “What I have to say about the social doctrine of the Church is from the viewpoint of a Catholic in politics applying my understanding of the problems of the day.”

Ryan’s $3.53 trillion budget doubles down on past proposals to overhaul Medicare and other government programs that are seen as politically sensitive. While the budget has little chance to become law, it draws a distinct contrast with Democratic views on spending.

That speech, along with other statements that put his budget into religious terms, led liberal Catholic groups to openly protest Ryan’s budget.

In particular, NETWORK, a group founded by 47 Catholic nuns that speaks out on social justice issues, went on a bus tour around the country to protest the Ryan budget.

In an interview with CNN, Sister Simone Campbell, the executive director of NETWORK, said Ryan has co-opted sacred Catholic teachings and twisted their meanings.

This line of attack will intensify in the coming months because of Ryan’s nomination, says Deal Hudson, a religion and politics expert who ran President George. W. Bush’s Catholic outreach in 2000 and 2004.

“I think the Catholic left will make this the drumbeat about Congressman Ryan,” Hudson said. “That is why it is so important for the campaign to effectively get out in front of this argument.”

According to Hudson, it is possible to defend the Ryan budget from Catholic attacks, it will just take a campaign that “realizes this is what they face."