But the idea that there is a sudden influx of transgender competitors who are dominating women’s and girls’ sports does not reflect reality — in high school, college or professionally. Sports associations like the N.C.A.A., which has promoted the inclusion of transgender athletes, have policies in place to address concerns about physical differences in male and female biology. The N.C.A.A., for example, requires athletes who are transitioning to female to be on testosterone suppression treatment for a year before they can compete on a women’s team.
Ms. Stelzer, who competes in a weight lifting league that does not allow transgender women to participate, says the point is to get ahead of what she and other activists believe will become a bigger issue. “We’re nipping it in the bud,” she said.
In high school sports, where conservative activists have focused much of their attention, policies vary widely. Some states pose no barriers to transgender athletes; some have policies similar to those of the N.C.A.A. that set guidelines around hormone treatment; others have outright bans or demand that students verify their sex if questioned.
Rarely has an issue that so few people encounter — and one that public opinion analysts have only recently begun to study in depth — become a political and cultural flash point so quickly. The lack of awareness creates an environment in which the real impact of transgender participation in sports can be overshadowed by hyperbole.
But the debate also raises questions — that ethicists, lawmakers and the courts are only beginning to address — about whether the decades-long effort to give women and girls equal opportunities in sports is compatible with efforts to give transgender people equal opportunities in life. A lawsuit in federal court in Connecticut brought by three high school runners who lost in competition against transgender girls will be among the first to test how nondiscrimination laws apply.
A mix of factors has helped social conservatives breathe new life into the issue: activists who agreed to give up on unpopular bills regulating public bathrooms; an awareness that women, not men, could be more persuasive and sympathetic advocates; a new Democratic administration that quickly moved to broaden and restore rights for transgender people that the Trump administration had eliminated; and a political and media culture on the right that often reduces the nuanced issue of gender identity to a punchline about political correctness.
Activists who have been fighting the anti-transgender efforts in legislatures and through the courts say the focus on school athletics is creating a false and misplaced perception of victimization.