The first thing you need to know on the subject at issue here is the definition of the term “bellwether.”
In a political context, the word usually is defined as “an indicator of trends.”
Therefore, to say that the Catholic vote has been a bellwether in recent presidential elections is merely to note that it’s been an indicator of the overall results. That doesn’t necessarily mean that the Catholic vote has been the deciding factor in any given presidential election.
Putting it another way, a candidate might fail to carry what had previously been a bellwether group of voters and still win the election. Of course, the group of voters at issue is then no longer a bellwether.
Putting it yet another way, it might be said that winners of presidential elections have always been the candidates who prevailed among my first and second cousins on my father’s side. But those cousins have never tipped the balance in a presidential election.
With all that in mind, check out what Chris Cillizza is SAYING about the Catholic vote:
Among Catholic registered voters, [Barack] Obama and [Mitt] 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…
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.