President Biden on his first day in office signed an executive order expanding protections for transgender students. On his sixth day, he repealed the ban on transgender members of the military. On his 16th day, he threatened sanctions against countries that suppress transgender rights.

And on his 37th day, his nominee for assistant secretary of health sat for a confirmation hearing to become the first openly transgender federal official confirmed by the U.S. Senate.

Biden is pursuing a little-noticed but sweeping effort to remake transgender rights in America, which in turn has sparked a conservative backlash and fed into Republicans’ efforts to portray Democrats as extreme on social issues. Among other arguments, conservatives are increasingly seizing on the much-disputed notion that embracing transgender rights threatens women’s sports.

“You can’t win against men,” said state Rep. Janel Brandtjen of Wisconsin, where a bill was introduced this week to ban transgender athletes in women’s sports. “That’s the biology, the reality. And, honestly, you’ll ruin women’s sports forever. Why would you compete if you knew you couldn’t win?”

Alphonso David, president of the Human Rights Campaign, said such assertions are baseless and dressed up solely for political purposes.

“It is not news that in 2021, transgender people are participating in sports consistent with their identity — this has been happening for decades,” David said. “Ask yourself, why is this only now a problem? It’s a problem because anti-equality forces understand their flawed rhetoric doesn’t work anymore. They need a target, and they need an enemy to mobilize their base.”

The intensifying battle over transgender rights reflects the tension over a range of issues that have little to do with Biden’s specific policies but reflect a belief that his presidency represents broader forces in American life.

Conservatives are expressing outrage, for example, that the toymaker Hasbro has decided to drop the “Mr.” from its Mr. Potato Head brand, leaving it gender-neutral. Republicans are excoriating the decision by Dr. Seuss Enterprises to stop publishing several of the author’s books that contain racially offensive images.

But it is Biden’s push to expand transgender rights that is emerging as a focal point for a Republican Party that remains divided on a host of other issues.

Nearly half of the states have pending bills that, like Wisconsin’s, would ban transgender athletes. House lawmakers in Mississippi on Wednesday voted overwhelmingly in favor of legislation that would ban transgender athletes in public women’s sports. The bill is expected to be signed into law by Gov. Tate Reeves (R), who last month criticized Biden’s transgender policies, saying they would harm athletes such as his daughters.

Senate Republicans have raised the topic repeatedly during confirmation hearings, with Sen. Rand Paul (R-Ky.) questioning Biden’s nominee for assistant health secretary, Rachel Levine, on transgender medical treatments while falsely asserting that puberty blockers can cause irrevocable changes.

Sen. Mitt Romney (R-Utah) raised concerns with Biden’s secretary of education about transgender athletes, pointing to his grandchildren.

“I’ve got pictures of my eight granddaughters, among some grandsons, behind me,” Romney said during a video hearing. “They shouldn’t be competing with people who are physiologically in an entirely different category.”

Former president Donald Trump, in his first major speech since leaving the White House, said on Sunday that Biden’s policies would “destroy” women’s sports. “If this is not changed, women’s sports as we know it will die,” Trump said. “They’ll end. It’ll end.”

Conservatives make little secret of their view that highlighting women’s sports is an advantageous way for them to frame the discussion, rather than debating the right of transgender people to be treated like everyone else.

Terry Schilling, executive director of the American Principles Project, has long been trying to shape a message on transgender policy for Republican political candidates. The group’s polling last year, he said, suggests that many voters — including Biden supporters and those who otherwise back LGBTQ rights — oppose letting athletes who were assigned male at birth compete in women’s sports.

“We found that the women’s sports issue was not only exceptionally powerful, but it also had the benefit of not being exclusive,” Schilling said. “It was something that our organization could convince politicians to champion.”

But transgender advocates say that in the 16 states that allow full inclusion of transgender students in high school sports, the dire warnings are not borne out by reality. “Last I checked, girls’ athletics did not vanish,” said transgender advocate Gillian Branstetter.

Fewer than 2 percent of U.S. high school students identify as transgender, according to data published in 2019 by the Centers for Disease Control and Prevention.

Virginia Del. Danica A. Roem (D-Prince William), one of the country’s first openly transgender elected officials, said Republicans’ focus on transgender rights is a strategic shift after they failed to block same-sex marriage. “When they start losing one aspect of a culture war, they turn gears,” Roem said.

The message, she added, threatens an already vulnerable group. “The more they do that . . . what happens?” Roem said. “They exacerbate an already existing toxic environment for kids.”

Transgender rights erupted as a national issue in 2016, when North Carolina enacted a bill restricting transgender people’s use of bathrooms that align with their identity. That created a backlash among businesses across the country, and the NCAA boycotted North Carolina until the bill was repealed.

White House officials say Biden entered office determined to alter the government’s approach to transgender rights, fulfilling promises he made during the campaign. He has been a frequent ally and family friend of Sarah McBride, who in November won a race in Delaware to become the country’s first transgender state senator.

Catherine Lhamon, deputy director of the White House Domestic Policy Council, said many of Biden’s moves aim to restore rights that previously existed.

“The rights have been there — the rights are not new,” said Lhamon, who focuses on racial justice and equity at the Domestic Policy Council. “We had an administration that for four years turned its back on some among us in a way that is reprehensible and appalling. This administration will not do that.”

Transgender rights have growing support, polls suggest. In a 2020 poll by the Kaiser Family Foundation, half of U.S. adults said society has not gone far enough in recognizing people who are transgender, while 15 percent said society had gone too far.

But polling does indicate a partisan split, with Democrats more likely to believe that someone’s gender can be different from their sex assigned at birth. Democrats are also far more willing to allow transgender people to use a bathroom that corresponds with their gender identity rather than their sex assigned at birth.

The shifts in public opinion could make the issue delicate for Republicans. One Republican strategist, speaking on the condition of anonymity to discuss a sensitive subject, said Americans’ greater acceptance of the LGBTQ community means the transgender debate is a “potent message” only within communities that are socially conservative or religious.

Republicans plan to target heavily Hispanic districts, especially those in South Florida and Texas that embraced Trump’s message of keeping America and its families safe, the strategist said.

Republican officials believe an ad they ran in Texas against Democratic House candidate Gina Ortiz Jones, who is a lesbian, helped sink her campaign in a largely Hispanic district on the border. It highlighted her support for allowing transgender soldiers in the military.

Republicans are also shaping their appeal to target suburban women and mothers. Schilling’s group is planning to target Democratic congresswomen who are former athletes — including Rep. Cheri Bustos (D-Ill.), a basketball and volleyball player in college — saying that they would have been less successful if they had faced transgender women.

A coalition of LGBTQ advocates is planning to launch a campaign to counter some of the Republican rhetoric, saying they will produce ads and lobby certain Republican senators to pass the Equality Act, a federal bill protecting LGBTQ rights.

They say the focus on women’s sports is the latest version of earlier, equally invalid arguments about same-sex marriage and transgender people’s use of bathrooms. “We are really accessing the best ways to engage with that narrative,” David said. “The narrative is just not true. It’s based on fear.”

Studies of transgender athletes are limited so far and based on small, narrow samples. LGBTQ advocates and health experts say that assertions about the biological advantages of transgender athletes fail to take into account the discrimination, trauma and other social hurdles that may affect a transgender athlete’s ability to compete.

Transgender advocates and pediatricians also say that the medical treatments that many transgender youths receive, including puberty blockers and hormones, can mitigate any physical disparities.

NCAA guidelines currently require at least a full year of testosterone suppression before a transgender woman is allowed to compete with other women. That guidance, published in 2011, noted that transgender women display a “great deal of physical variation, just as there is a great deal of natural variation in physical size and ability among non-transgender women and men.”

Much of the current debate has focused on the renewed push to pass the Equality Act, which would prohibit discrimination based on sexual orientation and gender identity. The legislation passed the House by a 224-to-206 vote, with three Republicans joining Democrats in support. It now heads to the Senate, where 10 Republicans would need to vote in favor if all Democrats support it.

During the House debate, Rep. Marjorie Taylor Greene (R-Ga.) called the legislation “an attack on God’s creation” and said it would mean that “men who dress and think they are women will have rights over all real girls and women.”

Rep. Marie Newman (D-Ill.), whose office is near Greene’s and who has a transgender daughter, placed a transgender flag outside her office, prompting Greene to place a poster outside her own office that said, “There are TWO genders: Male & Female. Trust the Science!”

The Biden administration recently withdrew from a Connecticut lawsuit aimed at banning transgender athletes from girls’ sports. The suit was filed by several runners who say they would have won state titles and had other opportunities but had to compete against two transgender sprinters. The Trump administration had signed on to the lawsuit.

Scott Clement contributed to this report.