Mark Wilson / Getty Images A woman participates in a protest outside the Hyatt Regency where Republican presidential candidate Mitt Romney was scheduled to attend a fundraiser March 22, 2012 in Washington.

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Americans may be more religious than their peers in other Western countries, but they have their limits when it comes to mixing religion and public life. According to a new survey conducted by Pew, a 38% plurality of Americans for the first time say there’s too much expression of faith in politics. That figure has increased dramatically in the last decade, especially in the last two years, and currently includes almost half of Democrats and independents. Even roughly a quarter of Republicans, up from 8% in 2001, feel the same way.

Part of this can be explained by the rise of the “nones”–Americans who do not identify with any particular faith or who consider themselves atheists and agnostics–a bloc that has grown considerably in recent years, from 12% of the population in the 1990s to 19% last year. Fully a third of young people now count themselves as unaffiliated, and young “nones” nearly doubled between 2006 and 2011, according to political scientists Robert Putnam and David Campbell.

In an article appearing in the March-April 2012 issue of Foreign Affairs adapted from their upcoming book, American Grace: How Religion Unites and Divides Us, Putnam and Campbell argue that the growth in the unaffiliateds has been fueled by a backlash against the religious right. There’s some debate whether the “nones” are really abandoning spirituality–most still believe in God but don’t claim ties to any organized religion–and whether culture warriors, secular indoctrination at elite institutions (as some conservatives dubiously argue) or pop evangelists (see Ross Douthat) are to blame.

But whatever the cause, the political implications of this bloc are plain: Unaffiliateds don’t like religious sermonizing in the public square. According to Pew, 66% of “nones” think the government is too involved in dictating morality; 70% think abortion should be legal in all or most cases; and 71% think homosexuality should be accepted by society.

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As you might suspect, a majority of the “nones” lean Democratic. But this story is not exclusively partisan. Since 2010, the proportion of white Catholics who say public figures are invoking faith too often has grown by the same amount, 11%, as it has among the unaffiliated, according to Pew. The increase among white mainline Protestants who feel the same way, a 13-point bump in the last two years, is even larger. However, white Evangelicals remain unswayed and heavily favor more religious politicking, not less.

That split is on display in the current Republican presidential primary, where religious expression appears to be something of a wedge issue. Mitt Romney has consistently performed well among the well-educated, a group more likely to shy away from political professions of faith, while every single major primary win by Rick Santorum has come in states where Evangelicals make up an outsize portion of the electorate.

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This is sometimes explained by Romney’s upper-class airs or Evangelical distrust of Mormonism — and Romney’s faith accounts for some of his reluctance to inject religion into the conversation — but Pew’s data show that a third of Romney supporters say there’s too much faith in politics (a 36% plurality says the current amount is OK) and a majority think churches should keep out of political matters. Pluralities of Rick Santorum’s backers, meanwhile, feel there’s too little religious expression and that churches should let their views be known.

Romney’s voters are still distinguishable from Democrats, an outright majority of whom say there’s too much religious expression in the arena, and if he wins the nomination, it’s unlikely to be a major factor in a contest between two men who lack strongly religious political identities. But the issue is not simply partisan. And the rise of the unaffiliateds indicates that it’s not one that’s likely to dissipate any time soon.

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