(RNS) Most ethno-religious groups in America have strong partisan preferences.

White evangelicals and Mormons are rock-ribbed Republicans. Latino Catholics and Jews are solid Democrats.

Once upon a time, white Catholics were solid Democrats too. Now they’re divided, tilting toward the GOP but subject to change. This year, they’ve bounced around remarkably in their presidential preferences, from supporting Donald Trump by as many as 36 points to supporting Hillary Clinton by as many as six.

Why isn’t partisanship built into white Catholic identity as much as it is into the other groups?

As a rule, swing voters are those whose policy preferences pull them in opposite directions. Consider this enumeration of issues from a new letter signed by Catholic women leaders:

Our faith calls us to affirm the sacred dignity of all life. This is why our Church defends life in the womb, the undocumented immigrant and the inmate on death row. As Pope Francis reminds us, we must also say no to an “economy of exclusion and inequality” that “kills,” and act to address environmental devastation that is disproportionately hurting the poor.

Though you’d never know it from listening to churchmen like Archbishop Charles Chaput of Philadelphia or the staff of the U.S. Conference of Catholic Bishops, Catholic social teaching pushes white Catholics more towards the Democrats than it does towards the Republicans.

READ: Archbishop Chaput welcomes ‘smaller church’ of holier Catholics

Not that there’s a shortage of Trump-supporting white Catholics — the 21st century version of Reagan Democrats.

But other than single-issue abortion opponents, white Catholics as Catholics have little reason to vote for an anti-immigrant, climate change-denying plutocrat like Donald Trump.

Come November 9, a majority of them will, I predict, turn out to have cast their ballots for Hillary Clinton.