Democrat Lucy McBath speaks during a rally for Democratic gubernatorial candidate Stacey Abrams at Morehouse College in Atlanta. McBath ousted Rep. Karen Handel (R) in a district in the Atlanta suburbs. (Alyssa Pointer/AP)

A gun-control activist whose son was fatally shot six years ago flipped a longtime Republican congressional seat outside Atlanta, underscoring Democrats’ strength in the suburbs and solidifying the party’s House win.

Lucy McBath, a 58-year-old first-time congressional candidate, had jumped late into the race against Republican Rep. Karen Handel in Georgia’s 6th Congressional District. Winning with 50.5 percent of the vote, McBath will join the new Democratic House majority from a district once held by former speaker Newt Gingrich (R).

“Ninety-eight Americans die every single day to gun violence,” McBath said in a statement. “To all survivors in this country — I stand with you. To every American concerned about the safety of their families — I pledge to fight as hard as I can for you and your family.”

The race was called the same day another mass shooting in California pushed the gun debate back into the news.

McBath’s victory came after a sweep of Democratic wins on Tuesday night put the party back in charge of the House starting in January. Her race had been too close to call, similar to roughly a dozen other House races that remained undecided on Thursday.

Democrat Kim Schrier was also declared the winner in Washington’s 8th District, beating Republican Dino Rossi to replace outgoing Rep. Dave Reichert (R).

From California to Maine, election officials continued the slow work of counting ballots in House contests where Republicans were defending seats. Democrats, who gained at least 30 seats, were expected to win five or six of the outstanding races.

Several Senate and gubernatorial races also were unresolved two days after the election.

In Florida, the outcomes of the Senate and governor’s races appeared in doubt. In Georgia, Republican gubernatorial candidate Brian Kemp claimed victory before an official call in his race against Democrat Stacey Abrams, whose campaign highlighted reports of voting irregularities. In Florida, a Republican led after a hard-fought Senate race that was too close to call, while in Arizona’s Senate race, the Democrat took the lead, although many more ballots remain to be counted.

On Thursday afternoon, five House races in California had not been called by the Associated Press, though a trailing Republican candidate had conceded in one.

Rep. Jeff Denham (R) led Democrat Josh Harder by about 1,200 votes in the 10th District, while Republican Young Kim had a 3,800-vote lead over Democrat Gil Cisneros in the 39th District. Rep. Mimi Walters (R) led Democrat Katie Porter by about 6,000 votes in the 45th District, and Democrat Harley Rouda led Rep. Dana Rohrabacher (R) by about 3,600 votes in the 48th District.

Rep. Steve Knight (R) conceded the race to Democrat Katie Hill in the 25th District, a longtime Republican stronghold.

It was possible, based on past elections, that vote counting might not be finished until next week or even later.

In Utah’s 4th District, Republican Rep. Mia Love trailed Democrat Ben McAdams by about 6,700 votes. In New Jersey’s 3rd District, Republican Rep. Tom MacArthur trailed Democrat Andy Kim by about 2,600 votes. In New York’s 22nd District, Democrat Anthony Brindisi led Republican Rep. Claudia Tenney by about 1,200 votes. And in North Carolina’s 9th District, Republican Mark Harris led Democrat Dan McCready by about 1,800 votes.

Republicans appeared to be hanging on in several competitive seats.

In New York’s 27th District, Rep. Chris Collins (R), who is under federal indictment, led Democrat Nate McMurray by about 2,900 votes. In Maine’s 2nd District, Rep. Bruce Poliquin led Democrat Jared Golden by about 1,900 votes. And in Texas, Rep. Will Hurd led Democrat Gina Ortiz Jones by about 1,100 votes.

Handel, who lost to McBath by about 2,900 votes, conceded the race as national news focused on a shooting at a country-music bar in Thousand Oaks, Calif. A gunman killed 12 people and apparently himself on Wednesday night.

As Democrats once again vowed to fight for “bipartisan, common-sense solutions” to prevent gun violence, McBath reflected on her political victory in light of the killings.

“It is unfortunately not surprising that on the very same day I officially became a congresswoman-elect, other families in this country are receiving the same exact call that I did six years ago when I learned my son had been murdered,” she said in a statement.

“As a congresswoman, but more importantly as a mother, I pledge to do everything I can to make our communities safer. The most important title I am ever going to hold is Jordan’s mom — and that is what drives me to keep going. Knowing firsthand the deep pain of losing a loved one to gun violence is what drove me to stand up,” she said.

McBath became an activist after her 17-year-old son Jordan was fatally shot in 2012 by a man who had argued with the teen and his friends about loud music coming from their car. She declared her candidacy after the February mass shooting at Marjory Stoneman Douglas High School in Parkland, Fla., that left 17 dead.

The history of her district, held by Republicans since 1979, made her win particularly meaningful for Democrats. In addition to being represented by Gingrich, it later elected Rep. Tom Price (R-Ga.), who left the House in 2017 to become President Trump’s first secretary of health and human services.

The race to replace Price, which pitted Handel against Democratic filmmaker Jon Ossoff, drew national attention as the first special House election following Trump’s victory and became a focal point for the emerging “resistance” movement, which hoped to demonstrate its power by turning a prominent red district blue.

Ossoff lost the race, though Democrats said that his campaign laid the groundwork for McBath’s victory.