RICHMOND — Schuyler VanValkenburg, a Democrat in the Virginia House of Delegates, drove the oak-shaded streets of his suburban district, pointing out landmarks that told the story of how he had won his seat after Republicans held it for decades.

Over there was one of the county’s first mosques. There, the Hindu Center. The Final Gravity Brewing Company had opened near Love Shack, a breakfast spot offering Virginia ham and eggs on a croissant.

The houses of worship for global immigrants and the cool watering holes for young transplants reflected sweeping demographic changes that have pushed politics in the Richmond suburbs, including Henrico County, to the left.

“A new generation moved in,” said Mr. VanValkenburg, a high school government teacher first elected in 2017. “Henrico became browner. It became denser.”

But now, he and his party are in races that are far tighter than most expected, including a deadlocked governor’s contest. And Democrats’ historic margins in Virginia in recent years are suddenly looking as though they may have been the result not of an inexorable demographic tide, but of a furious resistance to Donald J. Trump — one that exaggerated the true strength of the Democratic Party in a state that could be returning to its previous role as a battleground.

Without Mr. Trump in office, Terry McAuliffe, the former Democratic governor seeking a new term in that post, is fighting for his political life, four years after the current Democratic governor coasted to a 9-point win.

Greater Richmond, including the capital city and its diversifying suburbs, is the second-fastest-growing region in the state and a key to the governor’s race, as well as to control of the Legislature.

A poll released Wednesday by Christopher Newport University suggested that Democrats were falling well short in the region. While it mirrored most other polls in showing the governor’s race deadlocked statewide, it said Glenn Youngkin, the Republican candidate, had pulled away from Mr. McAuliffe in the Richmond media market — an area extending beyond the city and its populous suburbs into rural counties.

A Fox News poll on Thursday was even grimmer for Democrats: It showed Mr. Youngkin with an 8-point lead among likely voters statewide ahead of Tuesday’s election.

“On the ground, it feels like our side has all the energy,” said Mark Early Jr., a Republican vying for a Democratic-held seat in the House of Delegates that straddles Richmond and suburban Chesterfield County.

Mr. Early said a Youngkin television ad ripping Mr. McAuliffe for saying parents shouldn’t tell schools what to teach had poured “gasoline on the fire” of some voters’ frustrations over public schools, first kindled last year by Covid-related school closures that set back students’ learning. “I hear a lot of blowback from moms, especially working moms,” he said.

Democrats accuse Mr. Youngkin of distortions and fear-mongering on schools, including calls for police officers in every school and a ban on critical race theory, which educators say plays no role in K-12 curriculums.

Still, Mr. Youngkin’s forward-looking closing message, emphasizing “parents’ rights,” seemed considerably more resonant with voters than Mr. McAuliffe’s retrospective final appeal — reminding Virginians, whose swing counties are doing quite well economically, of all the jobs he created and the money he spent on education as governor from 2014 to 2018.

“If Youngkin is able to turn it around here, I think it will be because of his education gambit,” said Richard Meagher, a politics professor at Randolph-Macon College near Richmond. “That’s the one issue where you can still win back those suburban voters who have turned into the Democratic column lately.”

For Mr. McAuliffe to prevail in greater Richmond, Democrats need to drive up turnout in the city; maintain their gains of the past 15 years in Henrico County, north and east of the city; and not cede too much ground in Chesterfield County, which includes more conservative western suburbs.

On Thursday evening, Mary Margaret Kastelberg, a Republican challenging a Democratic delegate in a bellwether district in Henrico County, spent her 26th wedding anniversary knocking on the doors of residents her campaign had identified as swing voters.

She wasn’t having much luck.

Laura Kohlroser, still in hospital scrubs from her workday, said the Jan. 6 riots at the Capitol had deeply soured her on Republicans. “The way the Republican Party stood behind Donald Trump, that to me was just deplorable,” she said.

Walter Taylor said that he had been a “die-hard Republican” through 2016, voting that year for Mr. Trump, but that his shambolic presidency “turned me 180 degrees.” He was not convinced that Mr. Youngkin, a former financial executive, was really the hoops-shooting, fleece-vest-wearing regular guy he portrayed in TV ads.

“He’s too close to Trump,’’ said Mr. Taylor, a retired insurance underwriter. But Ms. Kastelberg earned his vote, he told her.

Earlier on Thursday, Mr. McAuliffe had been in Richmond for a rally with leaders of the African American community, which makes up 40 percent of the population. Early voting in the city has been running behind early voting in the suburbs, an imperfect but useful gauge of enthusiasm.

At a community center on the North Side, Frank Moseley, director of a nonpartisan group that informs voters of color about issues, said Democrats’ failure to deliver on big promises made to Black voters in 2020 — on gun violence, affordable housing and voting rights — had cooled some voters’ ardor. “We are probably one of the most letdown voting blocs,” he said. “That is one of the biggest detractors for individuals going out to vote.”

One of the few younger people in the room, Aja Moore, 24, acknowledged what polls are showing: Voters under 30, a big part of the Biden coalition last year, are less likely to vote now.

“They’re busy with their life,” said Ms. Moore, who works in government relations for a big law firm. “They’re not into it.’’

In an interview, Amy Wentz, a member of a civil rights group, the Richmond Crusade for Voters, suggested another potential reason that some Black voters, especially women, may be in a funk: The party nominated a 64-year-old white man for governor after he defeated two Black female legislators in the primary.

Ms. Wentz, who said she was a strong McAuliffe supporter, forwarded a Facebook post from a friend. “I know I am going to get fussed at, but I am not motivated to vote,” the woman wrote. “I really feel some type of way about Virginia not having a Black woman as our gubernatorial candidate.”

Ms. Wentz said Mr. McAuliffe had done a good job reaching out to people of color, including in a Zoom meeting with her own organization. “I feel like we’re going to step up,” she said. “We’re not feeling it right now, but I feel like that by Tuesday, people are going to do the right thing. There’s too much at stake.”

The 2020 census confirmed the demographic upheaval of the Richmond region. Within the city, which only last month removed the last Confederate statue — of Robert E. Lee — from historic Monument Avenue, the share of white residents rose over the past decade faster than any locality in the state. Gentrification has transformed industrial areas into neighborhoods of craft breweries and restaurants serving Alsatian cuisine.

At the same time, the Black population swelled in the suburbs: by 25 percent in Chesterfield County, its largest growth among all racial groups. In Henrico County, the populations of Black, Asian and Hispanic residents all rose significantly.

Mr. VanValkenburg, the lawmaker and teacher, said that 15 years ago, his students were overwhelmingly white. Now, about 100 languages are spoken in the county.

He rose to anger over Mr. Youngkin’s campaigning on issues involving education, including his stoking the cultural issue of critical race theory — a dog whistle to white voters that is not even taught in grade school — and accusing Democrats of wanting to keep parents out of classrooms.

“Of course parents should have a say in education,” said Mr. VanValkenburg, who emails parents weekly updates on their children’s class work.

Republicans, he complained, “keep trying to gin up issues that aren’t real as a way to scare people,” including appeals to conservatives who have led efforts to remove books with gay and racial themes from schools.

If Mr. Youngkin is elected and fulfills his pledge to ban critical race theory his first day, Mr. VanValkenburg said, it would have no practical effect. “But what it would do is create a culture of fear,” he said, driving through his district on Wednesday.

“Does somebody feel bad about their race if we teach about slavery?” he added.

On Thursday, the local paper reported that a parent had complained at a school board meeting about a novel in school libraries about an interracial teenage romance. Mr. VanValkenburg’s Republican opponent was quoted expressing his disgust. The district removed eight copies of the book from its shelves.