By Dan Gilgoff, CNN.com Religion Editor

Washington (CNN) - President Barack Obama has opened up a significant lead among Catholic voters, a crucial swing voting bloc, according to a recent Pew poll.

Obama leads opponent Mitt Romney among Catholic voters by 54% to 39%, according to the survey, conducted from September 12 to 16 by the Pew Research Center for the People & the Press.

Obama’s lead in the Pew survey comes despite outspoken recent criticism of the Obama administration from America’s Catholic bishops and despite Mitt Romney’s selection of a Catholic running mate, Wisconsin Rep. Paul Ryan.

The survey was released last week, but the findings on Catholic voters were highlighted this week by the Religion News Service, which notes that Obama held a much tighter 49-47% lead over Romney among Catholics in a June Pew poll.

John Green, a religion and politics expert at the University of Akron, said Obama’s gains among Catholic came from growing support among Hispanic and black Catholic voters, but also from white Catholics, among whom Obama is now tied with Romney.

Follow the CNN Belief Blog on Twitter

“That’s the part of the poll that I think is kind of surprising,” Green said, noting that Obama lost white Catholics in 2008, even as he won the overall Catholic vote.

Green said that it is white Catholics who were most likely to be receptive to the bishops’ recent attacks against the Obama administration over what the church says is the White House’s curtailment of religious freedom.

In its recent “Fortnight for Freedom,” campaign, the church urged American priests to denounce the administration’s requirement that health insurance companies provide free contraception coverage to employees, even if those employees work for Catholic organizations that oppose contraception.

“The bishops were hoping those efforts would bring more moderate and liberal Catholics, not necessarily for Romney but against the administration’s position,” Green said.

CNN’s Belief Blog: The faith angles behind the biggest stories

John Allen, CNN’s chief Vatican analyst, noted that at least one other recent national poll gave Romney a slight lead among Catholics, and that Romney leads among Catholics who attend Mass each week.

“That either shows that the more practicing you are, the more pro-Romney (or anti-Obama) you are,” Allen said in an e-mail message, “or it says something about the political message Catholics are getting in their parishes these days.”

Catholic voters, who accounted for more than a quarter of the electorate in the 2008 election, have voted with the winning presidential candidate in every election going back to the early 1990s.

In 2008, Obama beat John McCain among Catholics by 54% to 45%. In 2004, John Kerry - the first Catholic nominee for president since John F. Kennedy - lost the Catholic vote to George W. Bush, provoking Democrats to take Catholic outreach more seriously.

Both major parties had America’s highest-profile Catholic cleric, New York Archbishop Timothy Dolan, give the closing prayer at their recent political conventions.

The Democratic Convention also featured a Catholic nun who led a “nuns on the bus" tour attacking the federal budget that Ryan designed in his role as chairman of the House Budget Committee.

The Obama and Romney campaigns have both rolled out Catholic outreach efforts in recent days, and the Romney camp has highlighted Ryan’s Catholicism.

“A faithful Catholic, Paul believes in the worth and dignity of every human life,” Romney said when he introduced Ryan as his running mate last month.