The separation of church and state doesn't mean religious leaders can't express political opinions. And in the wake of President Obama's endorsement of gay marriage there has been talk that some houses of worship may encourage their flock not to vote for the president in 2012 to protest his reversal on the issue.

However, the majority of Americans would rather that churches and other religious institution keep out of politics altogether. According to a Pew Research Center Poll of 1,503 adults, 54 percent said that churches should keep out of political matters, whereas 40 percent think churches should express views on political questions.

In 1996, these percentages were just about reversed, with 54 percent in favor of churches being involved in politics and 43 percent opposed.

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