Surveys indicate that the Catholic vote is "too close to call," a Catholic research center at Georgetown University says.

"The vote of Catholics remains quite evenly split: 47 percent for President Obama and 45 percent for Gov. Romney," the Center for Applied Research in the Apostolate said Sept. 17.

The statistically tied candidates have rarely topped 50 percent of the Catholic vote. The small percentage of Catholic registered voters will likely decide the winner of the Catholic vote in a country where one in four voters is Catholic.

The research center aggregated data from polls that surveyed a Catholic sub-group, including Pew, Gallup and TIPP.

Among Protestants, Gov. Romney leads the president by 51 to 40 percent. Those without a religious affiliation largely favor the president, with 63 percent saying they will vote for him and only 27 percent stating they will vote for Romney.

Democrat President Obama has led Gov. Romney by nine percentage points once in March and once in July, while the Republican nominee had his biggest lead of five percentage points in April.

Catholic voters have long been considered an important voting bloc because the presidential candidate who wins over the majority of Catholic voters generally wins the election. However, some commentators question whether the "Catholic vote" exists given the divisions among Catholics.

The Nov. 6, 2012 presidential election is expected to be very close, with the two candidates vying to win every percentage point of the electorate they can to their corner.