The startling defection of a longtime Democratic lawmaker upended the balance of power in North Carolina on Wednesday, giving Republicans narrow veto-proof supermajorities in both chambers of the battleground state’s legislature.
The Democratic lawmaker, State Representative Tricia Cotham, announced in a news conference on Wednesday morning that she was becoming a Republican, saying she had been bullied by her fellow Democrats and had grown alienated from the party on issues like school choice.
“The modern-day Democratic Party has become unrecognizable to me and to so many others throughout this state and this country,” she said in a brief speech. She said both she and her young children had been subjected to personal attacks by Democrats in the state, and denounced what she called attempts to “control” her. “They have pushed me out,” she said.
Her declaration infuriated fellow Democrats and sent shock waves through North Carolina. A reliable Democratic vote when she served in the House from 2007 to 2017, she once stood on the House floor and shared her experience of having an abortion, calling it “a deeply personal decision” and accusing Republican lawmakers of “wanting to play doctor.”
Ms. Cotham, 44, whose district sits outside Charlotte, ran again successfully for the chamber in November on a platform of raising the minimum wage, protecting voting rights and bolstering L.B.G.T.Q. rights.
Now, however, her decision helps Republicans cement razor-thin but complete control over a second chamber of the legislature, giving them the ability to bypass Gov. Roy Cooper, a Democrat, and create a glide path for their legislative agenda. Republican leaders have indicated a desire to seek new restrictions on abortion and tighten the state’s voting laws, among other issues.
In the House, Republicans will have the 72 votes they need to override Mr. Cooper’s vetoes; they already have a veto-proof majority in the Senate.
Though Republicans have long controlled the legislature, they lost their supermajorities in both chambers in 2018, leaving Mr. Cooper with the ability to block G.O.P. bills. Since taking office in 2017, he has turned back more than 75 such measures.
The decision by Ms. Cotham to switch parties, first reported by Axios a day earlier, caught Democrats by surprise. As of Tuesday afternoon, Ms. Cotham had not spoken to Democratic colleagues about her plans, nor had she contacted State Representative Robert Reives, the party’s leader in the House, he said in an interview.
But by the afternoon legislative session on Tuesday, Ms. Cotham was seated on the Republican side of the chamber, with aides having cleaned her desk on the Democratic side. Her Twitter account liked a statement welcoming her to the Republican Party.
In introducing Ms. Cotham, Tim Moore, the Republican speaker of the State House, praised her as having a “bipartisan” streak, and characterized the defection as part of “a national move, where folks realize that there’s this wokeness” that “has pervaded in a lot of ways.”
In a statement on Tuesday, Governor Cooper said he was troubled by Ms. Cotham’s shifting allegiances.
“This is a disappointing decision,” he said. “Representative Cotham’s votes on women’s reproductive freedom, election laws, L.G.B.T.Q. rights and strong public schools will determine the direction of the state we love. It’s hard to believe she would abandon these long-held principles, and she should still vote the way she has always said she would vote when these issues arise, regardless of party affiliation.”
Mr. Reives, in a statement issued shortly after Ms. Cotham moved her desk in the chamber on Tuesday, accused his colleague of deceiving her constituents and called on her to step down.
“The appropriate action is for her to resign so that her constituents are fairly represented in the North Carolina House of Representatives,” he said.
Mr. Reives said in the interview that he was surprised by Ms. Cotham’s switch and that her political and family history indicated strong Democratic ties. In addition to her record of voting for Democratic priorities, her mother, Pat Cotham, was once a Democratic National Committee member.
How Ms. Cotham might vote on abortion was a particularly perplexing question for Democrats. When asked how she might vote on G.O.P. bills restricting abortion, she demurred and said that she could not comment on legislation that was not before her.
“I’m going to vote my conscience,” she said.
During a battle over an abortion bill in 2015, Ms. Cotham spoke on the House floor about having had an abortion.
“My womb and my uterus is not up for your political grab,” she said at the time, addressing Republican lawmakers. “Legislators — you — do not hold shares in my body, so stop trying to manipulate my mind.”
After reports of her party change emerged, Emily’s List, a national group that backs women who support abortion rights, issued a statement criticizing Ms. Cotham for “joining a Republican caucus that has stridently opposed abortion rights, rolled back voting rights and imposed deep cuts on public education for years.”
It added that “by changing parties and abandoning the principles that our community fights to uphold, Representative Cotham is no longer eligible” for the group’s support.
In recent days, there had been signs of a fissure between Ms. Cotham and Democrats. Her absence during a floor vote last week allowed Republicans to override Mr. Cooper’s veto of a bill removing a permit requirement for handguns. It was the first Republican override of Mr. Cooper’s veto since 2018.
Ms. Cotham faced some criticism from her Democratic colleagues over her absence. State Representative Cecil Brockman, a Democrat who also missed the floor vote during the veto override, said in an interview that “I didn’t see it coming, but I do get how she feels resentful from the constant character attacks that she has received, and a couple of us have received.”
He added: “It’s a lot of eating your own. The biggest issue with Democrats in the state of North Carolina is we’d rather be right than win elections.”
Ms. Cotham focused much of her remarks on Wednesday on what she described as a pattern of bullying at the hands of her colleagues. “Women in the House caucus,” she said, had “started vicious rumors that are very hypocritical of other stances that they make.” She also said that “interest groups and lobbying groups that are aligned with the Democrat Party have directly sent messages to my 12-year-old son” and recalled an incident where a woman loudly criticized Ms. Cotham and her son while shopping at Target.
Republicans in North Carolina have been looking beyond their immediate legislative agenda toward larger structural changes.
In November, the party reclaimed a majority on the State Supreme Court, giving it a 5-to-2 conservative lean and removing a key check on Republican lawmakers’ attempts to further gerrymander the state’s legislative and congressional maps. In February, the court moved to rehear two major voting rights cases — one striking down gerrymandered State Senate districts and another nullifying a voter identification law — that the justices had decided in the previous term.
If the court reinstates the Republican-friendly maps, it would be further entrench G.O.P. control of the state legislature in a state that is still competitive between both parties at the statewide level.
“It doesn’t come as a surprise to me, but it does shift total power to the state legislature away from the governor’s office,” Pat McCrory, a Republican former governor of the state, said of Ms. Cotham’s move.
Mr. McCrory recalled struggling with the Republican-controlled legislature when he was in office. “It was even tough on me as a Republican governor,” he said. “The issues weren’t philosophical. The issues were all about who has the power of appointments and, right now, they’re taking advantage of it. They’re taking away more powers from the governor’s office.”
In an email on Tuesday night, Ms. Cotham’s mother, Pat Cotham, who is a Mecklenburg County commissioner, urged her daughter’s critics to reserve judgment and said that her daughter “came to this decision with prayer and great reflection.”
“She is not afraid to stand alone,” she said. “I admire her courage in making this hard decision. I hope both parties encourage members of their caucuses to serve their constituents and collaborate with their colleagues with dignity and respect.”
Party switching is a real if rare phenomenon in American politics. In December, Senator Kyrsten Sinema of Arizona revealed that she was leaving the Democratic Party to become an independent, complicating her party’s narrow majority in Washington and raising the specter of an unpredictable three-way race for her seat in 2024.
And in 2019, a day after Representative Jeff Van Drew of New Jersey broke with fellow Democrats to vote against impeaching Donald J. Trump, he appeared in the Oval Office to declare his new status as a Republican and his “undying support” for the president.
Bitter feelings tend to follow such shifts in allegiance.
Matt Hughes, a Democratic National Committee member who described Ms. Cotham as a friend, said her party change contradicted the values shared by many Democrats.
“Tricia has always, in my view, been someone who has been supportive of L.G.B.T. rights and women’s bodily autonomy,” said Mr. Hughes, who is the mayor pro tem of Hillsborough, N.C., and one of a few dozen openly gay elected officials in the state, adding that he was “very disappointed” in the move.
Shelia Huggins, a Democratic National Committee member from North Carolina, said Ms. Cotham’s decision was a reminder that the state was still red, with pockets of blue.
“There are always those few people who register blue and say that they’re blue, but don’t always come through in the end,” Ms. Huggins said. “She knows what this change does.”
Kitty Bennett contributed research.