SOUTH BEND, Ind. - Taking a break from studying for final exams, three dozen Catholic students gathered for a barbecue on a grassy area of an apartment complex near the University of Notre Dame, their cellphones dialed in to a conference call with Victoria Reggie Kennedy, wife of Senator Edward M. Kennedy of Massachusetts.
She urged them to help turn out the vote in the Indiana Democratic presidential primary tomorrow for Senator Barack Obama, saying the candidate embodies the "Catholic social justice tradition" she was raised to believe in.
For about two months, pundits and analysts have been culling exit poll data from recent primaries to contend that Obama has a problem winning support from Catholic voters in his bruising struggle with Senator Hillary Clinton for the party's nomination.
Last week, a group of former national party chairmen who support Clinton drove home that point in a letter to members of the Democratic National Committee, part of a Clinton effort to stop the steady movement of superdelegates to Obama.
They wrote that Catholics are part of a Clinton electoral base that includes women, Hispanics, seniors, middle- and low-income Americans, and rural, suburban, and urban voters. They called it "a formidable coalition tailor-made for victory in a November general election."
But for both campaigns, the issue of Catholic voters reflects the reality of a Democratic electorate that has split along lines of class, race, gender, and age.
The gathering of Catholics for Obama near Notre Dame last week reinforced a perception that if Obama has a weakness among Catholics, it is with those who fit into other demographic subdivisions: women and older, less educated and lower-income voters, groups that Clinton has attracted.
Conversely, the group that met in South Bend represented Obama's demographic strengths among the more educated, affluent, and, except for a small group of Notre Dame faculty members who attended, younger voters.
After national elections in which the swing voting bloc has been variously identified by pollsters and commentators as the silent majority, Reagan Democrats, soccer moms, or football dads, 2008 is shaping up as the year that Catholics go under the media microscope.
"There is no one such thing as a Catholic voter," said Cathleen Kaveny, a professor of law and theology at Notre Dame, who attended the event in South Bend and is a member of Obama's national steering committee of Catholic advisers.
Catholics, who account for about 18 percent of the population of Indiana and a quarter of the national electorate, are much more diverse in the United States than they are often portrayed, Kaveny said. The challenge for Obama, she said, is to make Catholics more familiar with his message of economic empowerment, equality, and ending the Iraq war.
The South Bend area is a battleground in tomorrow's Democratic showdown, with characteristics favorable to both candidates. The city of about 105,000 is the seat of St. Joseph County, a blue-collar Democratic stronghold in the region known as Michiana along the Michigan-Indiana border. Like the neighboring city of Mishawaka, South Bend is heavily Catholic, with a history of ethnic parishes.
On the West Side, standing less than 100 yards apart are St. Patrick's Church, an Irish parish that celebrated its 150th anniversary on Saturday, and St. Hedwig's, a Polish parish built 19 years later. Not many years ago, congregations of Catholic immigrants from Belgium and Hungary worshiped at separate churches about a block apart in the same working-class neighborhood.
South Bend also has a large black population of about 24 percent, a significant Hispanic population of about 11 percent, according to US Census Bureau estimates, and a large academic community, centered around Notre Dame, the region's largest employer, a branch of Indiana University, and several smaller colleges.
In earlier contests, Obama beat Clinton among Catholics in states such as Iowa, Missouri, Louisiana, and Virginia, and tied in Wisconsin, exit polls showed. But in the later-voting big industrial states of Ohio and Pennsylvania, the data showed Clinton thumping Obama by 27 and 40 percentage points, respectively, among Catholics.
The Obama campaign disputes that those figures indicate a problem generally with Catholic voters, but it is making intensive efforts to reach out to Catholics. Last month it rolled out an advisory committee of about 50 prominent Catholics, including political figures, academics, and activists.
Last week's event in South Bend was one of many "Call to Family" gatherings of Catholics for Obama in Indiana, where supporters met and then phoned family and friends in the state. Emphasizing the importance of South Bend, Mark Linton, the Obama campaign's national Catholic outreach coordinator, attended the Notre Dame event.
Various theories have been offered by political analysts to explain Catholic voting patterns in a Democratic contest between candidates from Protestant traditions - United Methodist for Clinton and a black congregation of the United Church of Christ for Obama. Some are pseudo-psychological, such as older Catholics being comfortable with a female authority figure like Clinton because they were taught by nuns.
But two political scientists who have studied the role of religion in politics said the Catholic vote reflects a distilled version of other demographic trends that have emerged over the long Democratic battle.
"This is not so much about Catholicism as it is about other demographic factors," said John C. Green, a political science professor at the University of Akron and senior fellow at the Pew Forum on Religion and Public Life. "The Catholic vote tends to be older, more working class, and, in Democratic primaries, more female, so part of what may be going on here is less about Catholicism than it is about other social characteristics."
Green also theorized that the contrast between Clinton's stump style of stressing "a laundry list of particular policies" and Obama's "lofty rhetoric" may work to Clinton's benefit among Catholic Democrats, many of whom tend to support public solutions to social welfare problems.
"Not all that long ago, the Catholic community was basically a Democratic monolith, but that began to change in the 1970s and '80s, during the Reagan era," said David Campbell, a professor at Notre Dame who specializes in religion and politics.
Two of Obama's prominent Catholic supporters - Senator Robert Casey Jr. of Pennsylvania and former US representative Tim Roemer, who represented the South Bend area, say the media are oversimplifying the role of Catholics.
"I think it's overanalyzed, and a lot of it is poorly analyzed," said Casey, who like Roemer opposes abortion, breaking with Obama on that issue.
"Time is Barack's friend," Casey said. "The more voters hear him, the more they'll have confidence in him."
"You can't lump all Catholics into a particular box," said Roemer, president of the Center for National Policy, a Washington-based organization that researches national security and intelligence issues. "We have everything in the Catholic community from Opus Dei on the far right to liberation theology Catholics on the left and everything else in between."