When Mayor Lori Lightfoot announced a deal to bring NASCAR to Chicago’s downtown streets, the idea was met locally with surprise and bewilderment.

Chicagoans have a deep, if often unrequited, love for their sports teams, but a limited fluency in the world of stock car racing. NASCAR, for its part, had never sent its top drivers to race amid the sharp corners and manhole covers of city streets, mostly favoring neatly paved tracks in places like Daytona Beach, Fla., and Talladega, Ala.

However unlikely a union between the country’s most popular racing series and its third-largest city may have been, it is now a reality.

Grandstands are nestled along the tree line in Grant Park, Chicago’s front yard. Barriers are in place beside bus stops near the Art Institute. And come Sunday, drivers will blaze past Buckingham Fountain, turn toward the Field Museum and head to Michigan Avenue and Columbus Drive, traveling up to 140 miles per hour, more than quadruple the usual speed limit.

Still, many questions linger — about the high-decibel roar of racecars; about the potential for epic, city-snarling traffic jams; about whether NASCAR even belongs in Chicago.

“This is wonderful if you’re affluent and can afford to be part of it,” said Edgar Leslie, a resident of Chicago’s South Side, who said his city had more pressing concerns, like homelessness, than a car race where tickets start at $269 and reach above $3,000. “There are so many people who are not affluent and can’t afford to be part of it. What does that mean to those people?”

Two years ago, as new Covid variants kept American downtowns empty, NASCAR tried something novel: a simulated, televised race through a digitized Chicago. Without needing to leave home, the sport’s top drivers sped virtual cars down a course nearly identical to the one they will race on this weekend.

There were early murmurs in the NASCAR world that the online race might be the precursor to a live-action version. But making it happen would require selling the idea to a city not known as a bastion of motor sport fandom. Plus, racing on city streets, with their bumps and curbs and 90-degree corners, was a far cry from NASCAR’s usual straightaways and left turns.

Still, each side saw an opportunity.

The pandemic had been unkind to downtown Chicago. Commuters stayed home. Office spaces went dark. Two rounds of looting scared visitors away, as did a citywide homicide rate that soared to generational highs.

Bringing a car race to Chicago, city leaders said, had the potential to fill hotels, showcase the photogenic lakefront and attract race fans who live within a day’s drive but might be unlikely to visit otherwise.

“You think about some of the core demographics for who engages with NASCAR,” said Samir Mayekar, who served as a deputy mayor in Ms. Lightfoot’s administration, “and many of those demographics might have a different perception of Chicago. This is a chance for them to visit our great, world-class city and just see how amazing it is.”

NASCAR, which over the decades grew from a mostly regional series in the rural South to a national circuit with passionate fans, had its own pandemic-era problems.

There was a top driver suspended for using a racial slur. There was a call, which NASCAR heeded, from the only Black driver in the sport’s top series to ban Confederate flags at racetracks. There was a vulgar chant that NASCAR fans directed at President Biden, which gave rise to the “Let’s Go Brandon” slogan.

Racing in the streets seemed to offer a shift in the conversation and a way for NASCAR to try to make headway on its long-held goal of diversifying its fan base.

About 6 percent of Americans self-identify as avid NASCAR fans, according to the SSRS/Luker on Trends Sports Poll, down from a peak of 16 percent in 2004. White people made up about two-thirds of avid NASCAR fans in 2022, according to the poll, down 13 percentage points since 2004. The poll showed growth in the percentage of avid fans who were Black or Hispanic, up 10 percentage points since 2004 to make up about one-quarter of those fans in 2022.

Though NASCAR had raced before at a traditional speedway an hour from downtown Chicago, its leaders hoped to reach a new audience in the city, where there are roughly equal numbers of white, Black and Hispanic residents.

“When you look at any kind of sporting event, asking fans to drive, a lot of times, more than an hour away is kind of asking a lot,” said Joey Logano, a two-time NASCAR Cup Series champion who will race in Chicago. He said he liked the idea of “taking an event like this to the people — downtown — and making it where you really can’t get away from it.”

There are no guarantees it will succeed.

In interviews with drivers before a sold-out race in Madison, Ill., just outside St. Louis, most said they were looking forward to the Chicago event, even if they were unsure how it would go. Many had never raced on streets. Some admitted trepidation about tight passing zones and the potential for track-blocking collisions.

“Don’t know if it’s going to work — there’s a chance it doesn’t,” said Brad Keselowski, a former NASCAR champion who will race in Chicago. “But I respect the fact that we’re taking shots.”

Ms. Lightfoot announced a three-year deal with NASCAR executives last summer to bring auto racing to city streets. The grumbling followed almost immediately.

City Council members fumed that the mayor, who was then seeking re-election, had left them out of negotiations. Residents worried about noise, street shutdowns, potential damage to artifacts at the world-famous Art Institute of Chicago, and more.

Though running on city streets is a first for NASCAR’s Cup Series, it is not an entirely new concept. IndyCar races on the streets of Detroit and Nashville, among other places, while Formula 1, which has seen a surge in popularity in the United States, competes on courses along ordinary streets, including in Azerbaijan, Monaco and, later this year, Las Vegas.

After the announcement in Chicago, NASCAR set up a local office and began a charm offensive, explaining the basics of the sport to residents who had never seen a race.

They brought Chicago Public Schools students to the Field Museum to meet a driver and test their hand at a racing-themed engineering problem. They met with skeptical City Council members and neighborhood groups. And after working with the Art Institute to ensure that vibrations from the race would not put artifacts at risk, they unveiled a promotional car featuring Vincent van Gogh.

The community relations blitz earned the sport grudging respect from early skeptics and solidified support from residents who saw the race as a clear win for the city.

Liana Gissendanner, a resident of Chicago’s West Side and a fan of the driver Bubba Wallace, said she had long enjoyed NASCAR, though she said many of her neighbors were not as familiar with the sport.

“It’s a big deal; it’s definitely good for the community,” said Ms. Gissendanner, who was thinking about attending the race on Sunday afternoon, which is set to start at 4:30 p.m. Central time and air on NBC. She added, “I know people are complaining about the streets being shut down — that’s a big theme — but I think people are excited.”

But skepticism remains widespread, and patience for the long list of road closures has worn thin among residents whose commutes were already time-consuming.

“How safe is it to be running these cars up and down city streets when you’ve got people living on Michigan Avenue, on Roosevelt Road, just feet away from what’s going to be a racecourse?” said Leslie Recht, who leads a resident advisory council for Grant Park, the sprawling green space that the racecourse winds through.

If the weekend goes well, there is a chance that the event becomes a pivot point for NASCAR, which cannot easily build new tracks but could conceivably find streets to race on in most big cities. NASCAR has also held an event the last two years at the Los Angeles Memorial Coliseum, better known as a football venue.

“If we can prove out a stadium and prove out a street course,” said Ben Kennedy, a NASCAR senior vice president, “that unlocks the door for us to go to a lot of other markets.”

There is also a chance that the street race is a one-off.

Ms. Lightfoot, who brought the race to the city, lost her bid for re-election this year and left office in May. Her successor and fellow Democrat, Mayor Brandon Johnson, has been polite but circumspect about NASCAR, though he attended a pre-race event this week. He had little choice about proceeding with this year’s race, but after the checkered flag waves, he could seek to pull the city out of the rest of the contract.

“Will this idea lead to the expansion of how we think about what can be offered in a major city?” Mr. Johnson said in an interview shortly before his inauguration. “And if it has the ability to spark our imagination and create real opportunities for the people of Chicago, it becomes a baseline of whether or not we move forward with it.”

In other words, this weekend is a test.

“If they pull this off the first year and some of the naysayers and critics have to say, ‘Well, it turned out to not be so bad after all,’ then that’s going to pay off” for NASCAR, said Brian Hopkins, a Chicago City Council member who said he thought the economic benefits of the race had been overblown. “If, on the other hand, it goes badly, I think there will be pressure on the new mayor to cancel this deal.”