Social conservatives are growing more wary of church involvement in politics, joining moderates and liberals in their unease about blurring the lines between pulpit and ballot box, a new study found.

Fifty percent of conservatives think churches and other places of worship should stay out of social and political matters, up from 30 percent four years ago, according to a just-released survey by the Pew Forum on Religion and Public Life and the Pew Research Center for the People and the Press.

That significant shift in conservative thought has brought the country to a tipping point on the question: a slim majority of Americans (52 percent) now think churches should keep out of politics.

That's an eight percentage point increase over 2004 and the first time a majority of Americans has held that opinion since Pew officials started asking the question 12 years ago.

On this question, the gap between conservatives and liberals is narrowing: just four years ago, liberals were twice as likely as conservatives to say churches should stay out of politics. Now, 50 percent of conservatives and 57 percent of liberals think that. Four years ago, 62 percent of liberals opposed church involvement in politics. Democrats and Republicans are about even on the question, as well.

The survey also found largely unchanged attitudes along religious lines on the presidential choices compared with 2004, despite Democrat Barack Obama's strong play for religious voters and Republican John McCain's hesitancy to talk about his own faith and problems connecting with his party's evangelical base.

McCain leads Obama 68 percent to 24 percent among white evangelical Protestants, comparable to what President Bush was polling four years ago. But the support is tepid: just 28 percent of white evangelicals call themselves "strong" supporters of McCain, well short of Bush's 57 percent in 2004.

Changing attitudes about mixing church and politics could emerge as a factor in the fall campaign — particularly for McCain. Both campaigns are plotting get-out-the-vote efforts in faith communities, but past Republican successes came when attitudes were more welcoming.

The attitude shift cut across conservative constituencies: 46 percent of Republican Protestants want churches out of politics, up from 28 percent in 2004. Thirty-six percent of white evangelical Republicans hold that view, up from 20 percent four years ago.

The question asked specifically about places of worship, which by law cannot take stands for or against candidates or political parties but may speak out on issues. So the public might hold different views about political stances taken by religious leaders speaking as individuals or religious advocacy groups.

The findings come after midterm elections in 2006 that saw Democrats seize control of Congress, a landmark court ruling this year legalizing gay marriage in California, and also amid an identity crisis among conservative evangelicals about which issues should take priority and who speaks for the movement.

Among the groups that shifted strongly away from wanting to see churches involved in politics: Americans who are less educated, those who believe gay marriage is a very important issue and those who think the two major parties are unfriendly to religion.

"To my mind, that spells frustration," said Andrew Kohut, president of the Pew Research Center. "But by the same token, we know these very same people are not interested in less religiosity in the political discourse. They almost universally want a religious person as president.

"It's not that they want to take religion out of politics, it's that their frustrations with the way things seem to be going are leading them to say, 'Well, maybe churches should back off on this." '

The survey confirmed that white non-Hispanic Catholics, who make up about 18 percent of the electorate, are shaping up to be a big swing vote this fall: 45 percent support McCain, while 44 percent back Obama. Democrat John Kerry, a Catholic, was doing better at this juncture in 2004, winning 50 percent of those Catholics.

Asked which candidate "shares my values," 47 percent of all respondents replied Obama and 39 percent said McCain. White evangelicals favor McCain on that question, the religiously nonaffiliated leaned Obama, while white non-Hispanic Catholics and mainline Protestants were split.

Democrats have made inroads in closing the so-called God gap, at least by one measure: 38 percent of respondents said the party is "friendly toward religion," up from 26 percent two years ago. Even so, considerably more people — 52 percent — viewed the Republican Party as religion-friendly.