In an election where most of the attention has been on the Evangelical vote, the group that could help determine the result in the general contest is American Catholics.

Many American Catholics reside in the industrial heartland’s swing states, such as Pennsylvania, Michigan, and Wisconsin. They could make the difference for November 2008. In 2000, Vice President Gore barely edged out President Bush for the backing of Catholic voters. In 2004, President Bush beat Senator Kerry for the Catholic vote by 52 to 47.

Usually the question of the Catholic vote comes into consideration in the spring, once the primary season is over. This year is different. A major issue among the Republican candidates is electability. The focus is on which candidate will be the most likely to defeat the Democratic nominee. Senator Clinton has done well among upstate New York Catholic voters, a demographic that resembles other Rustbelt inhabitants. Mayor Giuliani is hinging part of his primary appeal on the fact that he can win a race against a Democrat.

Back in 2000, Raymond Flynn, a former Democratic mayor of Boston and ambassador to the Vatican in the Clinton Administration, caused a stir by endorsing George W. Bush over Al Gore. At the time, Mr. Flynn, who was president of the Washington-based Catholic Alliance, said he felt abandoned by the Democratic Party on a variety of issues, including trade, health care, and abortion. Now, Mr. Flynn, who travels around the country speaking to Catholic groups, says he senses his co-religionists returning to the fold. While the unpopularity of the war in Iraq is clearly an issue, also important are traditional economic issues that have moved Catholic voters in the past. “Right now, the so-called Reagan Democrat, they’re going Democrat,” Mr. Flynn, speaking from Rome, said. “Health care, education, human rights — these issues are so compelling in this election that they’re voting Democrat.”

Mr. Flynn says he has an anecdotal sense of Catholic’s political leanings from meeting them at speeches around the nation. That feeling may be supported by polling data. William D’Antonio, the coauthor of “American Catholics Today: New Realities of Their Faith and Their Church,” conducted a nationwide survey of Catholic voters along with the Gallup Poll. In Mr. D’Antonio’s sample, 82% of Democrats and 52% of Republicans, favored “more government funding to provide health care to poor children.” In the 2006 congressional elections, Democrats won 55% of the Catholic vote.

It’s very possible that many Catholic voters will move back to the Democratic Party on economic grounds and that a strong group of Catholic value voters will see no difference between Mr. Giuliani and the Democratic nominee of the abortion issue. Nevertheless, Mr. Giuliani’s advocates maintain that his biography and overall record in New York will enable him to thrive in the areas that are heavily Catholic.

A former governor of Massachusetts and ambassador to Canada in the Bush administration who has endorsed Mr. Giuliani, Paul Cellucci, says he sees Mr. Giuliani’s success among Catholic voters in New York City as a foreshadowing of what will happen in a presidential election. “I think that part of the voting population of which I’m obviously a member of is looking for a strong leader, somebody who’s going to keep America on offense against terror,” Mr. Cellucci says. “One of the things that will be important is the record the mayor had in cleaning up New York City. Forty-second Street was pretty sleazy and turned it into a place where families could go.” Mr. Cellucci adds that many Italian-Americans, a group that tends to be Democratic, he says, “are going to vote for Rudy.”

Given that the polling data suggests Catholics are moving back to voting Democratic in 2008, the question all the Republican candidates ought to be answering is which of these men can attract and retain the Catholic voter, not who can win over Evangelicals.

Mr. Gitell (gitell.com) is a contributing editor of The New York Sun.