Washington (AFP) - Millennial White House candidate Pete Buttigieg is no creature of Washington.

He was a virtual unknown before 2019, when he served as mayor of a mid-size Midwestern US city. He eschews the overt theatrics so ingrained in today's presidential politics.

As a technocrat who rarely raises his voice, Buttigieg deploys calm and reason over bombast, offering a center-left platform rather than political revolution.

And, he's gay.

At 38 years old he appears to have pulled off a political stunner: partial results show him winning the first vote in the 2020 presidential nominating contest Monday in Iowa, to seize the momentum in the race to see who faces President Donald Trump in November.

Last year Buttigieg entered a historically diverse field, competing against more seasoned candidates literally twice his age.

They include Joe Biden, the former vice president with an enviable political resume who has been the national frontrunner since entering the race, and Bernie Sanders, the great hope of the party's left wing who narrowly lost the 2016 nomination to Hillary Clinton and is seeking restitution.

Partial results suggest both political veterans were outperformed in Iowa by a youthful challenger with more military experience -- Buttigieg paused his mayoral duties to serve in Afghanistan as a US Navy intelligence officer -- and a composure that belies his age.

While Buttigieg appears to have beaten Sanders by the slimmest of margins, his fellow moderate Biden was left trailing far behind.

In an era of toxic division and high-pitched political noise, Buttigieg assures voters his breath-of-fresh-air status is not unique.

"Every time that my party has earned the White House in the last 50 years, it has been with a candidate who was new to national politics, focused on the future, not caught up in the ways of Washington, and opening the door to a new generation of leadership," he told a rally in Waterloo, Iowa.

"That's how we win."

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A key Buttigieg argument over the past year has been electability.

He stresses his progressive streak, but he believes that his more moderate positions on health care and taxes could win over voters in America's political middle, including independents and Republicans who voted for Trump and now want a way out of his divisive presidency.

Buttigieg has been quick to highlight how he has spent much of his recent Iowa stint seeking to win over counties that voted for Democrat Barack Obama in 2012 but flipped to Trump in 2016.

"We are welcoming into this effort an awful lot of what I like to call future former Republicans who are equally determined to turn the page," he said in Ottumwa on Sunday.

- Post-Trump unifier -

Translating his Iowa performance into broader electoral success will be a monumental task.

Despite impressive fundraising numbers he polls fifth nationally. Many Americans in later-voting states have seen little of Mayor Pete but far more of candidates with established national profiles.

And his failure to gain traction with a crucial Democratic demographic -- voters of color -- threatens to negate any momentum coming out of Iowa.

Voters at Buttigieg events often say his sexuality played little part in their decision-making.

But the issue may yet prove a hurdle: by way of illustration, after Iowa's tumultuous vote a viral video captured one Buttigieg supporter asking to change her vote upon realizing he was gay -- citing her religious beliefs.

In recent months Buttigieg, a former Rhodes Scholar who went to Harvard and speaks several languages, often focused more on his Christian faith than his same-sex marriage.

Chasten Glezman is a 30-year-old teacher who would become the first-ever "First Gentleman" if his husband were to win the White House.

As mayor, Buttigieg worked -- and sometimes clashed -- with Indiana's then-governor Mike Pence, a religious conservative who is now vice president.

For many Americans, Buttigieg was an unknown quantity until a televised town hall meeting last March when he slammed Pence as a "cheerleader" for Trump's "porn-star presidency."

As his campaign has grown, Buttigieg has positioned himself as a post-Trump unifier.

He supports health care expansion to all Americans, but unlike his more left-wing colleagues he proposes giving people a choice between a public option or private insurance.

He believes in strong labor unions and has suggested expanding the US Supreme Court to 15 justices.