Pete Buttigieg, the little-known Indiana mayor who has risen to prominence in the early stages of the 2020 Democratic presidential race, is expected to make his candidacy official during a rally Sunday in the city where he launched his political career less than a decade ago.

The 37-year-old Rhodes Scholar and Afghanistan war veteran, who has been exploring a White House run since January, plans a formal announcement that he’s joining the field of a dozen-plus rivals during a rally in South Bend, the town of roughly 100,000 where he grew up and is now serving his second term as mayor.

He will return this week to Iowa and New Hampshire, which hold the nation’s first nominating contests, to campaign as a full-fledged candidate now being taken more seriously.

Over the past few months, Buttigieg has appeared frequently on national TV news and talk shows and developed a strong social media following with his message that the country needs “a new generation of leadership.”

Buttigieg’s poll numbers have climbed. Some polls put him behind only Vermont Sen. Bernie Sanders, who sought the party’s nomination in 2016, and former Vice President Joe Biden, who has not yet said he’s running.

Buttigieg’s campaign has raised more than $7 million in the first three months of this year, a total eclipsed by Sanders’ leading $18 million but more than Sens. Elizabeth Warren of Massachusetts, Amy Klobuchar of Minnesota and Cory Booker of New Jersey.

FILE - In this Feb. 16, 2019, file photo, Mayor Pete Buttigieg, of South Bend, Ind., smiles as he listens to a question during a stop in Raymond, N. (AP Photo/Charles Krupa, File)
FILE – In this Feb. 16, 2019, file photo, Mayor Pete Buttigieg, of South Bend, Ind., smiles as he listens to a question during a stop in Raymond, N. (AP Photo/Charles Krupa, File)

“Right now, it’s pretty fun,” Buttigieg told The Associated Press last month while visiting South Carolina, where he was met by larger-than-expected crowds.

His challenge is finding a way to sustain the momentum over the long term and avoiding becoming a “flavor-of-the-month” candidate. Scrutiny of his leadership in South Bend has increased, as has his criticism of Vice President Gov. Mike Pence, who was Indian’s governor when Buttigieg was in his first term as mayor.

Buttigieg would be the first openly gay nominee of a major presidential party; he married his husband, Chasten, last year. He would be the first mayor to go directly to the White House. And he would be the youngest person to become president, turning 39 the day before the next inauguration, on Jan. 20, 2021. Theodore Roosevelt was 42 when he took office, while John F. Kennedy was 43 and Bill Clinton 46.

The campaign kickoff speech is expected to echo themes that have resonated with voters during Buttigieg’s exploratory phase.

He talks often about how political decisions shape people’s lives, including his own — from serving as a lieutenant in the Navy Reserve in 2014, to being able to marry his husband and to not having to worry about how to pay for his father’s hospital bills after his father’s death this year.

Buttigieg also says the best way for Democrats to defeat President Donald Trump may be to nominate a mayor experienced in helping to revive a Midwestern city once described as “dying,” rather than a politician who has spent years “marinating” in Washington.

He has criticized Trump’s campaign slogan, “Make America Great Again,” saying the way to move the country forward is not to look backward or cling to nostalgia or an old way of life.

South Bend, which neighbors the University of Notre Dame, was hit hard by the decline of manufacturing, dating to the 1963 closing of the Studebaker auto plant that costs thousands of residents their jobs.

The hulking, dilapidated factory loomed over the city for much of the past 60 years as what Buttigieg called a daily reminder of South Bend’s city’s past.

Buttigieg plans to give his speech inside that building, which underwent a multimillion-dollar renovation led by a private developer with help from state grants and tax increment financing from the city. The newly remodeled structure is now part of a mixed-use technology center outside the city’s downtown.