Cathy Willauer, who is Catholic and a mother of four, says her religion is important to her and she shares the same values as Rick Santorum.

But Willauer, 50, who lives in Annapolis, Md., has decided to support Mitt Romney instead of Santorum in Maryland’s Republican presidential primary on April 3. She said she had more confidence that Romney, the former governor of Massachusetts, could better manage the economy.

Besides, she said, Romney, who is Mormon, appears more tolerant of people of other faiths.

“While my personal values may align more closely with Senator Santorum’s,” she said, “I feel Governor Romney is more willing to tolerate different views and values, and the president of the United States has to accept and respect the right of every American to believe as they will.”

Willauer, who attended a Romney town-hall-style meeting in Arbutus, Md., last week, is part of a striking pattern that has emerged during the Republican primary season: More Catholic Republicans are favoring Romney even though Santorum is Catholic.

Santorum, a former senator from Pennsylvania, has trailed Romney among Catholics in 10 of the 12 states in which Edison Research conducted exit polls that asked about religion.

He has lost the Catholic vote by a minimum of 7 percentage points (in Michigan, where Romney grew up) and by as much as 53 percentage points in Massachusetts, where Romney was governor. He has even lost among Catholics in the South, although he was nearly tied with Romney among Catholics in Tennessee and won decisively among Catholics in Louisiana.

In most of the primary contests this year, whether he has won or lost, Santorum has been buoyed by the support of evangelicals. He has done best in states with substantial evangelical populations and they have become his most reliable base, along with some Tea Party supporters and those who call themselves very conservative.

In fact, many voters are unaware of his religion. A Pew survey this month found that only 42 percent of Catholic Republicans knew that Santorum was Catholic. At the same time, 11 percent of Catholic Republicans and 35 percent of white evangelical Republicans said they thought he was an evangelical.

“There’s an intensity to his statements, and to the subjects he discusses — the rise of secularism, the criticism of people of faith in the public square — that’s often associated with evangelicals,” said John C. Green, a political scientist at the University of Akron who studies religious voting patterns.

Analysts see many reasons for Santorum’s lag among Catholic Republican voters, the main one being that Catholics, who make up about a quarter of the total electorate, are not monolithic and are more representative of the electorate as a whole.

“There is no Catholic vote, per se,” said Catherine E. Wilson, a political scientist at Villanova University. “They mirror the general population, with progressives, moderates and conservatives. And Santorum is winning the conservatives.”

In 1960, Catholics voted overwhelmingly for John F. Kennedy. But in 2004, when Sen. John Kerry of Massachusetts became the first Catholic nominee since Kennedy, he lost the Catholic vote to President George W. Bush, a born-again Christian.

In 2008, President Barack Obama won the Catholic vote over the Republican candidate, John McCain. This year, Green said, Catholics appear likely to be divided again, with conservative Catholics voting for the Republican nominee, liberals voting for Obama and the moderates “up for grabs.”

So far, Romney, who has emphasized the economy, has been more successful in winning moderates over than Santorum, who has emphasized social, cultural and religious issues.

An important indicator of voting preference is how often someone attends church. Those who attend at least once a week tend to be more conservative than those who attend occasionally. But only about one quarter of Catholics attend church weekly.

Santorum was asked last week by Sandy Rios, a Fox News contributor hosting a program on American Family Radio, to explain why he was losing among Catholics.

He said he did not understand it himself — “I really wish I could tell you,” he said — but he said he thought it might correlate with church attendance, a traditional measure of religiosity.

“With folks who do practice their religion more ardently,” he said, “I tend to do well.”

In Louisiana, Joan Leon, 71, a retired nurse who voted for Santorum in Saturday’s primary there, would certainly qualify as an ardent Catholic. She attends church every day. Her chief concern is abortion — she so strongly opposes it that she goes to Washington regularly to march against it.

Leon braved a raging storm, floods and a tornado watch to see Santorum when he visited Mandeville, near her home. She said he is “the most pro-life candidate,” though she also likes his experience on the Senate Armed Services Committee and his support for more oil drilling.

“He’s willing to use our natural resources,” she said. “God gave us those resources to use, and we’re not utilizing them.”

But most Catholics disagree with Santorum on various issues, according to recent New York Times/CBS News national polls. A majority have used artificial birth control and few attend weekly Mass. Most support either same-sex civil unions or marriage, and only a few would prohibit abortions altogether. In his unsuccessful bid for re-election to the Senate in 2006, Santorum also lost the Catholic vote, by a lopsided 18 percentage points. He was running against Robert P. Casey Jr., also a Catholic.

Santorum’s faith-related comments have sometimes caused an uproar, as they did last month when he said he wanted to “throw up” after reading John F. Kennedy’s 1960 speech asserting that the separation between church and state be absolute. Even Santorum, rarely one to back off his heart-felt pronouncements, said he wished he had not used that language, but he stuck by his point, that people who try to express their faith in the public square are unwelcome and even persecuted.

The comment may have played a role in his narrow loss in Michigan, the first state to vote after he said it.

Wilson at Villanova said that by talking about matters of faith so often, Santorum appeared to be “more preacher than presidential contender,” which can make Catholics, among others, uncomfortable.

“People want politicians to have faith,” she said, “but they don’t necessarily want to be hearing about it all the time.”

A Pew study last week confirmed that view, showing that more voters than ever want less religious talk from politicians. It was the first time since Pew started asking that question a decade ago that more people said there had been too much religious expression from politicians, not too little.

When he ran for president in 2008, Romney felt compelled to address fears that the Mormon church would guide his policies. But this year, he has barely mentioned the subject. While some evangelicals remain suspicious of Mormons, Catholics like Willauer of Annapolis say they have no problem with it.

“Because Governor Romney is Mormon, a family man, I don’t take issue with his religion,” Willauer said. “I don’t know how the pope would feel about that, but we’re all modified Catholics these days anyhow.”

© 2012 The New York Times Company