Will Catholics decide this year’s election?

Maybe:

Ask ten people to name the most critical swing voting bloc in the 2012 presidential election and you’re likely to get at least five — and maybe ten — different answers.

But, new polling from Gallup suggests that it’s Catholics who could well be the best bellwether of whether President Obama or former Massachusetts governor Mitt Romney will be elected president this November.

Among Catholic registered voters, Obama and Romney each took 46 percent in 19 days worth of Gallup tracking polls between April 11 and April 30. The numbers among Catholics were a virtual mirror image of the head to head matchup among all registered voters where Obama took 46 percent to Romney’s 45 percent over that same time period. (Because of the large sample sizes — Gallup polled almost 2,000 Catholic registered voters over those 19 days — the numbers are even more reliable.)

It’s not just this presidential election where the Catholic vote serves as a leading indicator of the national vote.

In the five presidential races prior to this one, the candidate who carried the Catholic vote won four of them. The lone exception was in 2000 when then Vice President Al Gore won the Catholic vote by two points (and the popular vote by .5 percent) but lost the presidency to then Texas Gov. George W. Bush.

In fact, in the last two presidential contests the Catholic vote has tracked almost exactly with the popular vote. In 2008, President Obama carried Catholics by nine points and beat Arizona Sen. John McCain (R) by seven points nationally. Four years earlier, Bush won the Catholic vote by five points and beat Massachusetts Sen. John Kerry (D) by three points nationwide.

(It’s not just presidential elections where Catholics have been a key swing bloc. In the 2006 midterms when Democrats made huge congressional gains, the party won Catholics by 11 points. In 2010, when Republicans re-took the House, Catholics voted for GOP candidates by 10 points.)

In each of the past five presidential elections, Catholics have comprised somewhere between 26 percent and 29 percent of the overall electorate. (Catholics were 27 percent of the electorate in both 2004 and 2008.)

As Gallup’s Frank Newport notes in a memo on the findings, Catholics have historically been a Democratic-leaning constituency — the party can thank John F. Kennedy for that one — but in recent decades have become more of a toss-up voting bloc.

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