After a spokesman for the Obama campaign called it "the latest low," Mr. Santorum told reporters he was not suggesting that Mr. Obama was not a Christian. Mr. Santorum also criticized Mr. Obama's health care law over the weekend, in part because it requires insurance plans to offer free prenatal testing. "Free prenatal testing," he said, "ends up in more abortions and therefore less care that has to be done because we cull the ranks of the disabled in our society." "That, too, is part of Obamacare, another hidden message as to what President Obama thinks of those who are less able than the elites who want to govern our country," Mr. Santorum said. Mr. Santorum has said that as a Catholic, he opposes contraception. On Sunday, Mr. Santorum spoke to more than 3,000 people at First Redeemer Church here, and offered another statement that could prove controversial. In a long analogy, he compared the threat to Americans" freedom under Mr. Obama to the "great peril" of World War II and likened the present moment to the isolationist period when Americans were complacent about "this guy over in Europe." Unlike the challenge for the "greatest generation," Mr. Santorum said, there is no "cataclysmic event" to rally around. In his string of provocative remarks, some strategists see calibration. "Santorum knows exactly what he is saying and doing it for a reason," said Mark McKinnon, who was a strategist for President George W. Bush's campaigns. Santorum is too smart and too disciplined for his comments to be mistakes. His statements also might work by further eclipsing Newt Gingrich, his main rival for conservatives seeking an alternative to Mr. Romney. But some say there is a risk for him in the new scrutiny. "You get under the glare of that light," Mr. Castellanos said, and "a lot of people catch on fire."