The official purpose of Joseph R. Biden Jr.’s trip to Georgia in the final days of 2020 was to rally support for two Democratic Senate candidates facing tight runoffs. But the visit looked an awful lot like a victory lap.

“I have to say, it feels pretty good,” Mr. Biden told a crowd in Atlanta, reveling in the distinction of being the first Democrat to win Georgia in a presidential election in nearly 30 years. The moment — along with the Democrats’ win of both Senate seats a few weeks later, tipping control of the chamber — seemed to affirm the party’s resurgence in a state long dominated by Republicans.

This weekend, as Mr. Biden returns to Atlanta with ambitions of winning the state again in a rematch with former President Donald J. Trump, he faces a much different climate.

The optimism that soared among Georgia Democrats after his win has been overtaken by frustration and worry, not just about his campaign prospects but also about the direction of the country.

At Morehouse College, the prestigious Black institution where Mr. Biden is scheduled to deliver the commencement address on Sunday, some students urged school officials to rescind the invitation, and some faculty members have said they plan to skip the event — a signal of discontent over the president’s handling of the war in Gaza.

Beyond that, recent polls have shown Mr. Trump with a lead in Georgia, as support for Mr. Biden has softened among groups who had been instrumental to his success in 2020, including Black voters, other people of color and younger people.

“It’s definitely a void,” said Erick Allen, a Democrat running for a seat on the Board of Commissioners in Cobb County, just outside of Atlanta, referring to a “deficit of energy and funds in Georgia.”

Without other critical statewide races on the ballot, or the turbulence of the early pandemic or the racial justice protests that energized parts of the electorate in 2020, Mr. Allen said he worries about the level of interest and investment in Georgia.

“We don’t have a George Floyd, thank God,” Mr. Allen said. “We don’t have a Covid, thank God. Last election was in a crisis. We were dying in the streets and we were dying in the hospital beds. We’re not going to have that energy.”

For Mr. Allen and other supporters of Mr. Biden, those worries have not turned into despair. Some have noted that this time four years ago, Mr. Biden’s victory in Georgia was anything but assured. And voting rights groups like the New Georgia Project, which raised huge sums during the last campaign, were short on cash that spring, too.

In fact, many believe that Georgia has the potential to once again play an outsized role in what will almost certainly be a close and contentious election. The announcement this week that Atlanta will host the first of two televised debates between Mr. Biden and Mr. Trump has only solidified that notion.

“Georgia is still an important state,” said Yadira Sánchez, the executive director of Poder Latinx, a progressive civic engagement organization active in Georgia and other states with growing Hispanic populations.

Mr. Biden’s speech at Morehouse and the state’s primary election next week mark the beginning of the general election season — an occasion that has prompted some to re-examine the roots of the victories notched by Democrats in recent years.

Democrats had harnessed demographic shifts as the state’s population grew larger and more diverse, achieving significant gains among white, Black, Asian American and Latino voters in the rapidly expanding suburbs of Atlanta. There had also been years of groundwork to register and mobilize new voters, particularly young and poor voters of color who had historically been less likely to participate.

The evolution was evident during the governor’s race in 2018, when Stacey Abrams, a Democratic state lawmaker, made a strong showing against Brian Kemp, then the Republican secretary of state. Ms. Abrams lost by about 55,000 votes.

Two years later, that slow-moving transformation collided with a swift sequence of tumultuous national and global events that played out in Georgia in especially vivid ways.

The coronavirus pandemic magnified gaps in access to health care, and new political fissures opened over the government response. And the protests over racism and policing after Mr. Floyd’s murder in Minneapolis were especially intense in Atlanta. The killings of Ahmaud Arbery, a 25-year-old Black man, by white residents of a suburb on the Georgia coast, and Rayshard Brooks, a 27-year-old Black man, by an Atlanta police officer, escalated the anguish and fury.

“We were seeing the dawn of a new civil rights era,” said the Rev. Dr. Jamal Bryant, the pastor of New Birth Missionary Baptist Church in Stonecrest, a city of 60,000 just outside Atlanta where roughly 90 percent of the population is Black. With the Black Lives Matter movement, he said, young people were “finding their voice, their footing, and taking on a fight they did not initiate but they inherited.”

In the final weeks before the election, television and radio broadcasts were filled with political advertisements from across the spectrum while candidates, parties and civic groups had volunteers knocking on doors, making phone calls and sending messages by text and on social media.

It all drove a surge in turnout, and Mr. Biden beat Mr. Trump, who won most Georgia counties, by just shy of 12,000 votes.

The close margins spurred fresh turmoil: Mr. Trump and his allies tried to overturn his loss in Georgia by means that prosecutors considered criminal, leading to racketeering charges against them.

But the result also inspired jubilation, as the outcome — not just the Democratic victories but the level of participation — had once been difficult to fathom. “They chose to participate in making history,” said the Rev. Timothy McDonald III, the pastor of First Iconium Baptist Church in Atlanta. “We saw hope like we hadn’t seen it before.”

After the election, Republican state lawmakers passed sweeping legislation that added stricter requirements for voting by absentee ballot, limited the number of drop boxes for ballots and cut the amount of time between an election and a runoff.

Supporters, responding to Mr. Trump’s baseless claims that victory in 2020 had been stolen from him, said the measures would shore up the integrity of elections. But critics have condemned the new restrictions, which they say will have a disproportionate impact on voters of color.

Some in the Republican Party still refuse to concede that Mr. Biden won fairly. Others contend that the outcome was merely an aberration.

Heading toward November, Mr. Trump is benefiting from “the abject failure of the current administration” and a backlash to the criminal cases against him, which are “attempting to criminalize political disagreement,” Joshua McKoon, the chairman of the Georgia Republican Party, told reporters on Friday.

Democrats are concerned that voters may not have the stamina to turn out like they did before. “I think folks understand the importance of the election but there is a certain — just fatigue,” said State Representative Sam Park, a Democrat representing Gwinnett County, in the Atlanta suburbs.

Activists and others said that many 2020 Biden voters have grown disillusioned. There is anger over Mr. Biden not confronting Israel more forcefully over its actions in Gaza, and dissatisfaction over persistent issues like high housing costs and student loan debt.

Yet some supporters of Mr. Biden argue that the president’s problem is not a lack of achievements, but a failure to effectively explain them to voters. They point to the low levels of Black unemployment, the torrent of federal funds sent into communities for pandemic relief and infrastructure, and the administration’s efforts to cancel student loan debt.

“Those things ought to not be secrets,” said Bishop Reginald T. Jackson, the presiding prelate for the African Methodist Episcopal Church in Georgia, which has hundreds of congregations in the state.

The Biden campaign plans on heeding that advice, deploying high-profile Democrats — including Georgia’s senators, Raphael Warnock and Jon Ossoff — to drive up enthusiasm.

“Not saying that this is easy,” said Quentin Fulks, Mr. Biden’s principal deputy campaign manager and a Georgia native. “But I do think that we have a formula that’s conducive to accepting that message.”

Mr. Biden made sure to tout his record when he called into an Atlanta radio station’s morning show on Wednesday. He mentioned the creation of new jobs, investments in historically Black colleges and universities, and capping the cost of insulin — a potent issue in a state with elevated rates of diabetes.

He also pushed back against Mr. Trump, who has made some inroads with Black voters but lacks a campaign infrastructure in the state. Mr. Biden accused Mr. Trump of inflaming racial divisions, saying that Mr. Trump’s brand of politics was “all about hate, retribution.”

Leslie Palomino voted for Mr. Biden four years ago, the first time she’d voted in a presidential election. Back then, she also knocked on doors in Gwinnett County, on streets not far from where she grew up. She even had the chance to introduce Kamala Harris at a campaign stop.

The energy was palpable. So were the stakes.

Something similar could be possible this time, too, she said.

Poder Latinx, where she is the Georgia program coordinator, and organizations like it have started ramping up. And a lot can unfold between May and November, as 2020 proved.

“I’m counting down those days,” Ms. Palomino said, referring to the 24 weeks until Election Day. “I know our people — we’re resilient, and that’s what’s carrying me through.”