Her shift reflects how rank-and-file Republicans — even those who may disagree with him — have decided it is too perilous to openly challenge former President Donald J. Trump.MOUNT PLEASANT, S.C. — Representative Nancy Mace had just delivered the kind of red-meat remarks that would ordinarily thrill the Republican voters in attendance here on a recent sweltering evening, casually comparing liberal Democrats to terrorists — the “Hamas squad,” she called them — and railing against their “socialist” spending plans.But asked to give an assessment of her congresswoman, Mara Brockbank, a former leader of the Charleston County Republican Party who previously endorsed Ms. Mace, was less than enthusiastic.“I didn’t like that she back-stabbed Trump,” Ms. Brockbank said. “We have to realize that she got in because of Trump. Even if you do have something against your leaders, keep them to yourself.”Ms. Brockbank was referring to Ms. Mace’s first weeks in office immediately after the Jan. 6 riot, as the stench of tear gas lingered in the halls of the Capitol and some top Republicans were quietly weighing a break with President Donald J. Trump. Ms. Mace, a freshman congresswoman, placed herself at the forefront of a group of Republicans denouncing Mr. Trump’s lies of a stolen election that had fueled the assault and appeared to be establishing herself as a compelling new voice urging her party to change its ways.But these days, as Republicans in Congress have made it clear that they have no intention of turning against Mr. Trump, Ms. Mace has quietly backpedaled into the party’s fold. Having once given more than a dozen interviews in a single day to condemn Mr. Trump’s corrosive influence on the party, Ms. Mace now studiously avoids the subject, rarely if ever mentioning his name and saying it is time for Republicans to “stop fighting with each other in public.”After setting herself apart from her party during her first week in office by opposing its effort to overturn President Biden’s victory, Ms. Mace has swung back into line. She joined the vast majority of Republicans in voting to oust Representative Liz Cheney from leadership for denouncing Mr. Trump and his election lies. She also voted against forming an independent bipartisan commission to investigate the Capitol riot.And rather than continuing to challenge party orthodoxy, Ms. Mace has leaned in to the most combative Republican talking points, castigating Dr. Anthony S. Fauci, the top health official who is a favorite boogeyman of the right, accusing Democrats of forcing critical race theory on children, and publicly feuding with progressives.Her pivot helps explain why the Republican Party’s embrace of Mr. Trump and his brand of politics is more absolute than ever. It is not only the small but vocal group of hard-right loyalists of the former president who are driving the alliance, but also the scores of rank-and-file Republicans — even those who may disagree with him, as Ms. Mace has — who have decided it is too perilous to openly challenge him.“She’s a little bit like a new sailor; she tried to get her sea legs, but she’s also looking out over the horizon, and what she saw was a storm coming in from the right,” said Chip Felkel, a veteran Republican strategist in South Carolina. “So she immediately started paddling in another direction. The problem is, is that everything you say and do, there’s a record of it.”Ms. Mace declined through a spokeswoman to be made available for an interview, but said in a statement that “you can be conservative and you can be a Republican and be pissed off and vocal about what happened on Jan. 6.” (Ms. Mace’s most recent statements regarding the Capitol attack have been explanations of why she opposed commissions to investigate it.)“You can agree with Donald Trump’s policies and be pissed off about what happened on Jan. 6,” Ms. Mace said. “You can think Pelosi is putting on a sideshow with the Jan. 6 commission and still be pissed off about Jan. 6. These things are not mutually exclusive.”Ms. Mace is facing a particularly difficult political dynamic in her swing district centered in Charleston, which she won narrowly last year when she defeated Joe Cunningham, a Democrat. Her immediate problem is regaining the trust of the rock-ribbed conservatives who make up her base. It is all the more pressing because political observers expect Republicans to try to redraw Ms. Mace’s district to become more conservative, and possible primary challengers still have a year to decide whether to throw their hats in the ring.Her predicament bubbled below the surface on a recent evening here at a pork-themed “End Washington Waste” reception overlooking the Charleston Harbor and the docked Yorktown, a decommissioned Navy aircraft carrier. Voters signed the hocks of a paper pig urging Democrats to cut extraneous spending from the infrastructure bill and exchanged printed-out “Biden bucks” for cocktails, as some reflected on Ms. Mace’s balancing act.Ms. Mace campaigning in Mount Pleasant, S.C., in November. She is facing a difficult political dynamic in her swing district centered in Charleston.Mic Smith/FR2 AP, via Associated PressFrancis and Clea Sherman, a married couple who braved the 90-degree heat to attend, praised her for being “unafraid to speak out” and “tackling tough issues.”“We absolutely think that is the most horrifying thing — not to ever happen, but certainly one of them,” Ms. Sherman said of the Capitol breach, quickly adding that she was just as outraged by racial justice protests around the country that had grown violent. “All those riots that went along in all those cities — they’ve got to stop.”Mr. Sherman, a Korean War veteran, nodded along. “It was a shame it had to happen,” he said of the Jan. 6 assault, adding that he used to “get very upset” with some of Mr. Trump’s remarks.But the former president had been effective, he said. “In my whole life I’ve never been able to see someone accomplish so much,” Mr. Sherman added, citing low unemployment rates and a strong economy. “The bottom line was, did he get the job done?”Penny Ford, a Mount Pleasant resident who attended the event with her husband, Jim Ford, gave a more grudging assessment, explaining that they had winced at Ms. Mace’s comments about the former president. Still, she said, the congresswoman was “the best we have at the moment.”Ms. Ford said they would prefer to be represented by someone like Representative Jim Jordan of Ohio — a staunch Trump loyalist who helped plan the challenge to Mr. Biden’s election in the House — or Senator Ted Cruz of Texas — who led the effort to invalidate it in the Senate — and said they would consider voting against Ms. Mace next year “if I had a choice for someone else.”The first woman to graduate from the Citadel, Ms. Mace based her winning 2020 campaign on her up-from-the-bootstraps biography, detailing her journey from scrappy Waffle House waitress to statehouse representative. She bested Mr. Cunningham, who had been the first Democrat to hold the seat in nearly four decades, by just over a percentage point.On the campaign trail, Ms. Mace walked a careful line, balancing her libertarian streak with a more pragmatic approach, playing up a history of “speaking up against members” of her own party and “reaching across the aisle.”And in the days after the Jan. 6 attack, she was unsparing in her language. What was necessary, Ms. Mace said then, was nothing short of a comprehensive rebuilding of the party. It was a time for Republicans to be honest with their voters, she said: “Regardless of the political consequences, I’m going to tell the truth.”She could not stay silent, Ms. Mace insisted.“This is a moment in history, a turning point where because of my passion for our country, for our Constitution, for the future of my children — I don’t have that option anymore,” she said in an interview the day after the attack. “I can pick up the mantle and try to lead us out of this crisis, or I can sit idly by and watch our country go to waste. And I refuse to do the latter.”Ms. Mace in 1997, during her freshman year at the Citadel, where she became the first woman to graduate two years later.Paula Illingworth/Associated PressLess than a week later, her tone abruptly changed. After joining Representative Alexandria Ocasio-Cortez, Democrat of New York, in a bipartisan request to provide congressional staff aides with more resources to cope with the “trauma” of the Jan. 6 attack, she criticized her colleague for recounting how she feared that rioters had broken into her office building.“No insurrectionists stormed our hallway,” Ms. Mace wrote on Twitter, touching off a heated back-and-forth.She then fund-raised off the feud, arguing that “the actions of the out-of-control mob who forced their way into the Capitol” were “terrifying” and “immediately condemned by the left and right,” but that “the left,” particularly Ms. Ocasio-Cortez, had “run wild because they will never let a crisis go to waste.”More recently, when she voted against the formation of the proposed bipartisan Jan. 6 inquiry, Ms. Mace called the endeavor a “partisan, duplicate effort by Speaker Pelosi to divide our nation.”And after initially refusing to tell reporters whether she voted to oust Ms. Cheney, of Wyoming, from her No. 3 leadership post, Ms. Mace’s team issued a statement affirming that she had, saying that Republicans “should be working together and not against one another during some of the most serious socialist challenges our nation has ever faced.”Ms. Mace has, in some ways, retained her independent streak. She verbally slapped down Representative Marjorie Taylor Greene, Republican of Georgia, for comparing mask mandates to Nazism. And she has continued to work across the aisle with Democrats on issues like presidential war powers and cybersecurity.Her still-frequent appearances on television, though — now mostly on a variety of Fox News shows, as well as the conservative networks OAN and Newsmax — tend to stick to some of the party’s most well-tread political messages. In a recent interview on Fox News, she asserted that strident liberals had seized control of the Democratic Party.“They’re in charge,” she said, “which is why we’re seeing what we thought would be a moderate administration take a sharp left turn all of a sudden.” More