On Wednesday, in an interview in London, Gov. Scott Walker of Wisconsin, a potential Republican presidential candidate, sidestepped the question of whether he believed in evolution.

“I’m going to punt on that one,” he said to an audience at a research organization in London, which he was visiting for a trade mission. “I’m here to talk about trade, not to pontificate on other issues. I love the evolution of trade in Wisconsin.”

Mr. Walker’s response was not all that surprising — evolution is a sensitive issue for the evangelical Christian base of the Republican Party and presidential candidates have had to tread carefully around it.

The theory of evolution may be supported by a consensus of scientists, but none of the likely Republican candidates for 2016 seem to be convinced. Former Gov. Jeb Bush of Florida said it should not be taught in schools. Former Gov. Mike Huckabee of Arkansas is an outright skeptic. Senator Ted Cruz of Texas will not talk about it. When asked, in 2001, what he thought of the theory, Gov. Chris Christie of New Jersey said, “None of your business.”