SOUTH BEND, Ind. — Pete Buttigieg, the 37-year-old mayor of this northern Indiana city who in just weeks has vaulted from being a near-unknown to a breakout star in the Democratic Party, officially started his presidential bid here on Sunday, presenting himself as a transformational figure who is well positioned to beat President Trump, despite being young and facing off against many seasoned rivals.

“I recognize the audacity of doing this as a Midwestern, millennial mayor, but we live in a moment that compels us each to act,” Buttigieg said in front of thousands of supporters, jacket-free with his sleeves rolled up. “It calls for a new generation of leadership.”

Buttigieg added, “It’s time to walk away from the politics of the past and toward something totally different.”

The scene for Buttigieg’s rally was a hulking former Studebaker assembly plant, whose closure decades ago rocked this region’s economy. The site has since become a data and education hub pushed by his administration — and central to his technocratic, hopeful pitch that he is ready to help communities still struggling with the effects of globalization.

The Washington Post traveled to South Bend, Ind., to talk to locals about Mayor Pete Buttigieg joining the crowded field of Democrats running for president. (Joyce Koh/The Washington Post)

“Change is coming, ready or not,” Buttigieg told the crowd. “There is a myth being sold to industrial and rural communities: the myth that we can stop the clock and turn it back,” and he touted his attempts in the city to assist the workforce with training and skills programs.

Some attendees drove from around the country after being inspired by Buttigieg’s message and the historic nature of his campaign as a gay presidential candidate.

For Buttigieg, Sunday’s upbeat gathering on a dreary, snowy mid-April afternoon was an important political juncture: a reintroduction to a party that has only begun to pay attention to this mayor with a hard-to-pronounce name, but is now certainly listening closely as it searches for a standard-bearer.

Following a string of buzzy podcast and television appearances, increasingly crowded stops in early voting states, and the release of a best-selling memoir, Buttigieg is suddenly a contender in a crowded Democratic field, with a $7 million fund­raising haul in the first quarter of the year and a rapid rise in the polls.

Meanwhile, his husband, Chasten, has become a favorite of Democrats on social media, and Buttigieg has landed on the cover of national magazines, including New York magazine this week, with the headline “How about Pete?”

As rain fell on this city of roughly 100,000 on Sunday morning, thousands lined up under umbrellas and bundled up in jackets, waiting to enter the facility, holding homemade signs and carrying coffee cups and copies of his book, “Shortest Way Home.”

One of them was Ashley Pawlowski, 34, a self-described independent from South Bend who works at a local nonprofit. “The South Bend we all grew up in was very different. He changed this city and brought a new attitude,” she said. “He’s got this ability to help people deep down in his bones.”

Buttigieg’s challenge in the coming months: translating this meteoric momentum and goodwill among Democrats who are eager to cheer a confident, youthful voice from the Midwest into a sustained national campaign that can outpace candidates whose careers have made them popular with activists and donors.

Buttigieg has worked to rub off the heavy sheen of implausibility from his upstart candidacy, insisting that being a two-term mayor of a city in the middle of the country gives him more governing experience than Trump and that he is the face of a new generation that wants to bypass the partisanship and rancor that has gripped Trump’s Washington.

“My face is my message,” Buttigieg often tells voters on the campaign trail, a catchall way of referring to a calm persona that has drawn comparisons to President Barack Obama and to his own political profile: a gay Midwestern mayor, a retired Navy officer who served in Afghanistan and a Rhodes scholar who, if elected, would be the youngest president in U.S. history.

Buttigieg’s path will be anything but a glide. While some once-unknown outsiders, such as Jimmy Carter in 1976, have captured the Democratic nomination, others with electric starts have seen their bids fade.

Buttigieg has generated a swell of enthusiasm among several top Democrats and Obama allies, such as veteran strategist David Axelrod — and Buttigieg has met privately with Obama, who has praised him. Other Democrats remain muted about the mayor.

In recent days, Buttigieg’s record in South Bend has come under scrutiny. His administration’s efforts to knock down blighted houses in the city have been criticized by some Democrats as a policy that was overly aggressive in revamping lower-income areas that are home to many minority voters. South Bend also continues to grapple with a quarter of the city hovering on the poverty line.

Buttigieg’s record on race has drawn criticism from Democrats as well, particularly his demotion of South Bend’s first black police chief, Darryl Boykins, in 2012. Buttigieg has cited a federal investigation of Boykins as his rationale for the ouster, but Boykins went on to sue the city for racial discrimination.

Solomon Anderson, a 57-year-old banker from South Bend, said some in the city’s black community remain unsettled by Buttigieg’s handling of that incident, even as he and others cheered on the mayor’s campaign at the rally on Sunday.

“Not everyone is over it,” Anderson said. “He has tried to be a healer, to be inclusive, but it hasn’t always been easy.”

Axelrod, watching Buttigieg’s crowd from afar, noted on Twitter that the crowd “seems very large, very impressive but also very white — an obstacle he will have to overcome.”

And Buttigieg’s 2015 comment that “all lives matter,” which has been called insensitive by those in the Black Lives Matter movement that seeks to address issues facing black Americans with law enforcement, prompted him to reassure a civil rights group this month that he understands their concerns and stands in solidarity with their cause.

Buttigieg’s campaign is aware of the growing spotlight on his mayoral decisions and is determined to showcase his record and make the case that running a city like South Bend enables him to understand vexing national issues from a ground-level perspective. Sunday’s rally featured introductory speeches from mayors from other states who have become allies, following Buttigieg’s work in mayoral groups and his unsuccessful run for Democratic National Committee chairman in 2016.

“The horror show in Washington is mesmerizing. It’s all-consuming. But starting today, we’re going to change the channel,” Buttigieg said.

Nan Whaley, the mayor of Dayton, Ohio, called Buttigieg “the polar opposite in every way to Donald Trump.” Steve Adler, the mayor of Austin, endorsed him and said it seemed as though “the world is arriving in South Bend.”

Underscoring themes of generational change and his interest in reaching out to religious voters and working-class voters who drifted toward Trump have been priorities of Buttigieg and his aides as they have mapped out his campaign, believing he can make overtures to them and liberal Democrats at the same time.

The energy surrounding Buttigieg was evident over the weekend here: His campaign headquarters in South Bend was bustling with volunteers, who streamed past a wall painted with tall-lettered guidance on how to pronounce his name: “Boot Edge Edge.” Chasten Buttigieg greeted supporters and shared a playlist of songs from bands such as Fleetwood Mac and Phish for those taking road trips.

“5 years ago I came out to my family,” tweeted one supporter, Matthew Miller. “I never thought 5 years ago I’d be driving 8 hours through the night with my Republican father right by my side to go see the first openly gay man announce he’s running for president.”

Buttigieg’s policy proposals have been relatively broad compared to others in the field and so far tethered to his belief that American democracy needs to undergo a systemic renewal that includes a debate over possible changes to the U.S. Constitution, including expanding the Supreme Court and making the confirmation process less partisan and eliminating the electoral college.

On Sunday, he spoke out against the rise of white nationalism, voter disenfranchisement, gerrymandering and the influence of corporate money in campaigns.

“Sometimes a dark moment brings out the best in us,” Buttigieg said.