Allowing Republicans to claim the mantle of Catholicism might cost the Democrats the election. As commentators have noted, Catholics may be the nation’s most numerous swing voters.
Sure, but every time a commentator notes the powerful Catholic swing vote, another commentator replies that calling a particular demographic a bloc of swing voters is a dubious move—unless they tend to all vote together, which Catholics certainly do not. Maybe their Catholicism makes them swing voters, or maybe they're simply a representative mix of Republicans, Democrats and independents who happen to be Catholic. What's the difference, for anyone except the opinion writers?
You can call Paul Ryan a good Catholic and Joe Biden a bad one; you can say the opposite; you can call them each a cafeteria Catholic; you can argue that one of them better represents the core of Catholic teaching. Or you can say that Ryan's a conservative reformer and Biden's a mainstream Democrat, and that each of them is also Catholic and sometimes uses Catholic language to defend his positions.
We've been arguing for years about whether there's such thing as a "Catholic vote," in part because it's not an easy question to answer.