WASHINGTON -- Republican presidential hopeful Mitt Romney on Saturday denounced "poisonous language" against faiths as he grappled with a flare-up over religion sparked by a prominent supporter of Texas Gov. Rick Perry, his rival. Mr. Perry steered well clear of that simmering issue and pushed another hot button instead: Social Security.

Mr. Romney, in remarks to the Values Voters Summit, a gathering of cultural conservatives in Washington, did not directly confront the words of a prominent Mr. Perry supporter who called Mr. Romney's Mormon faith a "cult." Indeed, Mr. Romney was criticizing another speaker at the meeting who is known for anti-Mormon and anti-Muslim rhetoric, and who followed him on stage.

But his cautionary words served as notice that attacks on faiths should, in his view, be off the table. He appealed to the social conservatives to support a presidential candidate who has the best record on the economy.

Until now, Mr. Romney's Mormon faith and Mr. Perry's evangelical Christianity were secondary to a GOP primary focused on who can best fix the country's economy. Questions about his faith plagued Mr. Romney's 2008 presidential run, but he had been able to keep them at bay so far this time.

That changed when a pastor who introduced Mr. Perry to cultural conservatives called Mormonism a "cult" and said Mr. Romney is "not a Christian," forcing Mr. Perry to distance himself and Mr. Romney to respond. The back-and-forth suggests the primary race -- with a field finally settled and just three months before voting begins -- has moved into a more aggressive phase. And it illustrates that Mr. Perry's very public religiosity and long history with evangelical Christian leaders won't remain on the sidelines of the presidential race.

But Mr. Perry, campaigning Saturday in Iowa's staunchly conservative northwest, barely touched on religion at all. In stops at Sioux City and Orange City, he never mentioned Mormonism, Mr. Romney by name, or even Christianity, for that matter.

Asked by Republican Steven Bernston what books have most influenced him, Mr. Perry mentioned only one: the work of conservative economist Friedrich Hayek. Mr. Bersnton, a corn and beans farmer from Paullina, later said he was surprised that Perry didn't at least mention the Bible.