Stacey Abrams, who earlier this year was on a short list of potential vice-presidential candidates, was ultimately not chosen by Joseph R. Biden Jr. But on Friday, as Mr. Biden took a narrow lead in Georgia, it was Ms. Abrams who was celebrated, a sign of her remarkable ascent as a power broker since her failed bid for governor of that state two years ago.

Celebrities, activists and voters across Georgia credited Ms. Abrams with moving past her loss — she came within 55,000 votes of the governor’s mansion — and building a well-funded network of organizations that highlighted voter suppression in the state and inspired an estimated 800,000 residents to register to vote.

“You have to build the infrastructure to organize and motivate your base, and you have to persuade people,” said Jason Carter, a Democrat who was the party’s candidate for governor in 2014. “Stacey built that infrastructure, and Donald Trump’s presidency energized that infrastructure, and it opened up voters to persuasion who were previously not open, particularly in the suburbs.”

Mr. Biden pulled ahead of President Trump in Georgia, a state that has not elected a Democratic presidential candidate in nearly three decades, and maintained a slight lead throughout Friday. He was up about 4,100 votes Friday evening with more than 98 percent of the ballots counted. Because of the small margin, the secretary of state confirmed there would be a recount.

Still, Democrats in the state were jubilant.

State Senator Jen Jordan, a Democrat, said Ms. Abrams had built upon her loss by recognizing Georgia’s population growth, and its increasingly diverse demographic, as an opening for Democrats.

“She saw it coming,” Ms. Jordan said in an interview Friday. “The data was there if you wanted to look at it. The problem was nobody was really willing to look at the data.”

By bringing attention to the possibilities in Georgia, Ms. Jordan continued, Ms. Abrams attracted money to the state and used it to boost Democratic politicians. The organization has also distributed money to other state Democratic parties, particularly in the South.

Donors to her organizations have included labor unions and former New York Mayor Michael R. Bloomberg.

“She really put the spotlight on Georgia, convinced the people that needed to be convinced that there was room here, that there were voters here, and that this place really was competitive if people would just put in the time, the money and the effort in to do that,” Ms. Jordan said.

Ms. Abrams fought hard in 2018, and when she lost, she refused to concede. Her opponent, Brian Kemp, was then serving as Georgia’s secretary of state, the top election officer, and had spent years aggressively purging the state’s voter rolls and battling civil rights groups over ballot access. Mistrust lingers over that race.

“I, for one, feel she would be our governor if it were not for the rampant voter suppression tactics,” said Nikema Williams, the state’s Democratic Party chair who on Tuesday emerged as the victor to succeed John Lewis in the U.S. Congress. “The work that she did in organizing people on the ground, in coalition with other progressive organizations, was critical to building the infrastructure in this state.”

Ms. Abrams declined to comment on Friday. But in a tweet, she wrote, “My heart is full.” And she cited the work of other activists. “Georgia, let’s shout out those who’ve been in the trenches and deserve the plaudits for change.”

If Mr. Biden holds onto his slim lead in Georgia, her profile is likely to grow.

Mr. Carter, the grandson of former President Jimmy Carter who lost by eight percentage points, said Democrats had “hit a partisan ceiling” in the state. But “since 2014, Stacey’s effort, and others, have raised that partisan ceiling” by broadening appeal to younger voters, people of color and suburban residents.

After her loss in 2018, Ms. Abrams described that election as nonetheless a victory of sorts, as she had garnered more votes than any Democrat in Georgia history. Still, she acknowledged the pain, telling an interviewer that she “sat shiva” for 10 days, a reference to the Jewish mourning ritual.

Then she moved on to building a network of organizations that has become a well-funded juggernaut for voting rights and economic advancement. While some on the right have criticized her as a divisive figure, and her growing profile is not uniformly welcomed in the state’s Black political circles, there is general agreement that she has driven voters, particularly Black voters, to the polls.

In addition to fund-raising for a voter-protection initiative, Ms. Abrams’s organization has assisted Democratic state legislative candidates, whose campaigns have long been in legislative districts drawn by Republicans.

Ms. Abrams, a former minority leader of the Georgia House, founded the New Georgia Project while she was still in the state legislature. The nonprofit registered about 100,000 new voters. She then founded Fair Fight Action, an organization geared at combating voter suppression.

Since then, her network, headquartered in Atlanta, has grown into a varied network, including Fair Fight PAC, a SuperPAC that collected more than $33 million this election cycle. There’s also Fair Count, which promotes the census, and the Southern Economic Advancement Project, an organization whose mission is broadening economic power and building a more equitable future for underserved communities.

It is a mission deeply personal to Ms. Abrams, whose parents met in high school in Hattiesburg, Miss., and studied at Tougaloo College, a historically Black school near Jackson, Miss., before becoming Methodist clergy members. Ms. Abrams, 46, holds a law degree from Yale and worked as a tax lawyer before entering politics. She also has an affinity for Star Trek.

Her organization’s work against voter suppression was made more urgent by her defeat two years ago, and her allegations that suppression had played a role. Since then, Fair Fight has been a lead plaintiff in a federal lawsuit against the Georgia secretary of state in an effort to broaden access to voting. The suit takes aim at the state’s voter purges, its use of exact signature matching, and how it handles provisional ballots and its closing or relocation of polling sites.

Last year, Georgia reinstated 22,000 voters it had purged amid legal pressure from the group.

“This litigation has functioned as a significant point of pressure for the secretary of state and the state Board of Elections to make sure that Georgia’s election system is functioning the way that it should be,” said Jonathan Diaz, legal counsel for voting rights at the Campaign Legal Center, which is representing Fair Fight in the case.

Not everyone is celebrating Ms. Abrams. Lee Morris, a Republican who serves as county commissioner in Fulton County, home to Atlanta, said he viewed Ms. Abrams, a fiery orator, as “divisive,” drawing a comparison between her and Mr. Trump.

“Like President Trump’s allegations of cheating and corruption have fired up the right side, certainly her efforts have fired up the enthusiasm of folks to get out and vote,” Mr. Morris said in an interview Friday. That said, while Mr. Trump’s false claims of rigged elections and widespread cheating are baseless, Georgia has a long and documented history of voter suppression, particularly among voters of color.

Ms. Abrams has, at times, also run afoul of members of her own party, who criticized her blunt ambition and open desire to be Mr. Biden’s running mate. In the South, where Black politicians are close-knit and traditional, Ms. Abrams has also been a disruptive force. Her political vision can be at odds with the local Democratic establishment, and her shot to national prominence has ruffled feathers.

The political payoff of Mr. Biden’s breakthrough in Georgia, however, may put those tensions to rest. The playbook she popularized took root — a combination of winning back metro suburbanites and registering new voters in Black, Latino, and Asian-American communities.

Nse Ufot, the current chief executive of New Georgia Project, said electoral campaigns are often too shortsighted to do the long-term work of registering and educating new voters, regardless of party affiliation.

“When you think about the transactional nature of electoral campaigns, I think they prioritize getting people who are already voters to vote for them,” Ms. Ufot said, adding that there was “not enough conversation about 100 million Americans who are eligible to vote who did not vote in 2016.”