Like Romney and Santorum, he blasted Obama's contraception policies without delving into details of the latest changes.
"This administration is waging war on religion," said Gingrich, who grew up as a Protestant but converted to Roman Catholicism. "I frankly don't care what deal he tries to cut," he said of Obama. "He will wage war on the Catholic Church the morning after he's elected. We cannot trust him."
Santorum, a Catholic with a strong record of fighting legalized abortion, said Obama is "telling the Catholic Church that they are forced to pay for things that are against their basic tenets and teachings."
"It's not about contraception, it's about economic liberty," he said.
Romney, a Mormon who once supported legalized abortion, vowed to reverse "every single Obama regulation that attacks our religious liberty and threatens innocent life."
His critics cite a 2005 interview in which Romney said rape victims deserved either access to or information about so-called morning after pills that some see as a form of abortion.
All three GOP candidates restated their standard criticisms of Obama. Romney called him "the poster child for the arrogance of government."
Associated Press writers Kasie Hunt and Laurie Kellman contributed to this report.
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