The ruling stripped them of an issue they had used to galvanize rank-and-file supporters and big donors. And it left them searching for a cause that — like opposing gay marriage — would rally the base and raise the movement’s profile on the national stage.

“We knew we needed to find an issue that the candidates were comfortable talking about,” said Terry Schilling, the president of American Principles Project, a social conservative advocacy group. “And we threw everything at the wall.”

What has stuck, somewhat unexpectedly, is the issue of transgender identity, particularly among young people. Today, the effort to restrict transgender rights has supplanted same-sex marriage as an animating issue for social conservatives at a pace that has stunned political leaders across the spectrum. It has reinvigorated a network of conservative groups, increased fund-raising and set the agenda in school boards and state legislatures.”