Jenny Costa Honeycutt, a Charleston County councilwoman and lawyer, won a Republican primary runoff election on Tuesday for a House seat in South Carolina currently held by Representative Nancy Mace, according to The Associated Press.

Ms. Mace, an outspoken Republican who has a knack for making headlines and has shifted from moderation to staunch support of President Trump, lost her bid for governor this month.

Ms. Honeycutt defeated Mark Smith, a state representative, in a runoff after the two candidates advanced this month out of a crowded and chaotic field in the Republican primary.

The district, which hugs the southern coast of the state, leans significantly Republican, and Ms. Honeycutt is likely to be the favorite to prevail in November. But Democrats will try to make the race competitive: House Majority PAC, the main House Democratic super PAC, has reserved $2.1 million in the district for the fall, according to AdImpact, a media tracking platform.

“We look forward to supporting the Democratic candidate in SC-01,” said CJ Warnke, a spokesman for House Majority PAC.

Before 2020, the district briefly became something of a battleground. But in that year’s election, Ms. Mace clawed it back from a Democratic incumbent, and Republicans redrew the boundaries in 2021 to make it easier for Republicans to hold the seat. Ms. Mace won the elections in 2022 and 2024 by double-digit percentages.

Though Ms. Mace has often courted attention, the race to replace her took place largely under the national radar, with little polling or attention from Washington. Mr. Trump did not offer an endorsement, and no major outside spending group swooped in with millions to push any candidate. Ms. Honeycutt spent only about $155,000 on ads, according to AdImpact. She did receive a boost from the Winning for Women Action Fund, a Republican-aligned group that spent just under $500,000 in support of her.

“I’ve got 28 seconds to tell you what I stand for,” Ms. Honeycutt said in one of her ads, introducing herself as a mom, a business owner and a proven conservative. “No new tax increases. Make Trump tax cuts permanent and pass a balanced-budget amendment. Fix our infrastructure.”