(Reuters) - Pete Buttigieg, the millennial-aged mayor of South Bend, Indiana, who has enjoyed a surge in opinion polls and a torrent of media coverage, formally launched a bid on Sunday for the 2020 Democratic presidential nomination.

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“It is time to walk away from the politics of the past and toward something totally different,” he said at a launch event in South Bend.

No potential contender in the burgeoning Democratic field has seen as rapid a rise in the early stages of the campaign as Buttigieg, who has gone from obscure Midwestern politician to top-tier contender in a matter of weeks.

At 37, Buttigieg becomes the youngest entrant in a field that features 77-year-old U.S. Senator Bernie Sanders of Vermont and, likely soon, 76-year-old former Vice President Joe Biden - a contrast Buttigieg has embraced.

“I recognize the audacity of doing this as a Midwestern millennial mayor,” he told the crowd. “More than a little bold —at age 37 — to seek the highest office in the land.”

The man known as “Mayor Pete” has styled himself as the voice of the millennial generation, often talking about what the United States might look like decades from now.

“I take that long view because I have to,” Buttigieg said. “I come from that generation that grew up with school shootings as the norm, the generation that produced the bulk of the troops in the post-9/11 conflicts, the generation that is going to be on the business end of climate change for as long as we live.”

Buttigieg is the first openly gay major presidential candidate, which has given him inroads into a Democratic base that increasingly values diversity and progressivism.

During the event, he frequently mentioned his husband, Chasten, and spoke of the struggle to legalize same-sex marriage.

“Our marriage exists by the grace of a single vote on the U.S. Supreme Court,” he said.

As mayor of South Bend since 2012, he has presided over an economic turnaround that has brought new investment into the struggling northwestern Indiana industrial town, an achievement likely to be a central plank of his presidential campaign.

Indeed, his kick-off event was held inside the cavernous former plant that once made Studebaker autos. It closed in 1963 and only now is being redeveloped.

Polls of voters in Iowa and New Hampshire released last week showed Buttigieg in third place in both early-voting states, although still well behind Biden and Sanders. Buttigieg raised $7 million in the first quarter of the year, surpassing more established rivals such as U.S. Senator Elizabeth Warren of Massachusetts.

More than a dozen Democrats have announced a run for the chance to take on President Donald Trump, a Republican, in the November 2020 general election. Democratic voters will begin the process of selecting a nominee in a series of contests beginning early next year.

A former Rhodes Scholar, consultant for the firm McKinsey and Co and U.S. Navy reservist who served in Afghanistan, Buttigieg has the kind of background that could appeal to both moderates and progressives in the party.

But questions will persist about whether the mayor of an Indiana city of 100,000 residents is ready to run a nation of 330 million.