Patrick Ruffini, webmaster for Bush/Cheney ‘04 site, quotes an article that demonstrates the significance of the Catholic vote this election,

Bush’s strong performance among Catholics, it turns out, was crucial to his victory. Bush won Catholics 52%-47% this time, while Al Gore carried them 50%-46% in 2000. If Kerry had done as well as Gore, he would have had about a million more votes nationwide. According to Gallup Polls, only one Democrat since 1952 (Walter Mondale in 1984) lost the Catholic vote by this large a margin.

The Catholic impact was starker in key states. In Ohio, Bush got 55% of the Catholic vote in 2004 compared to just under 50% of them in 2000. That means a shift of 172,000 votes into the Republican column. Bush won the state by just 136,000 votes this year.

In Florida, Catholics made up 26% of the electorate in 2000. This year, they made up 28%. In 2000, 54% of Catholics went for Bush; in 2004, 57% of them voted for him. The combination of those two factors meant a gain of 400,000 voters in the Sunshine State—about Bush’s margin of victory.

Bush also did better among Hispanic Catholics, getting 42% of the vote in 2004 compared to 31% in 2000.