“We look like Camp Christian out here,” said Doug Gross, a Republican activist and former nominee for governor. “If Iowa becomes some extraneous right-wing outpost, you have to question whether it is going to be a good place to vet your presidential candidates.”

While social conservatives have long wielded a greater influence in Iowa than in many early-voting states, a bitter fight here over same-sex marriage and feuding rivalries among some of the state’s conservative leaders have amplified the issues and might help define the message of Republican candidates in ways that could resonate nationally…

“Social conservatives could fragment, creating an opportunity for a fiscal conservative to sweep the field with people who aren’t as concerned with social issues,” said J. Ann Selzer, whose firm here conducts the Iowa Poll and other state and national public opinion surveys. “All candidates are going to have their fiscal credentials vetted.”…

“I haven’t been asked too much about fiscal issues,” Mr. Paul said in a brief interview after speaking to parents who home-school their children. He added, “Focusing on only social issues will make a weaker candidate, not a stronger candidate.”