WASHINGTON — A gay veteran. A Louisiana political scion. And the chief executives of the nation's two largest cities.

As the U.S. Conference of Mayors opens its annual conference in Washington this week, all eyes will be on the unofficial four-man class of mayors who may run for president in 2020.

That's because these mayors — Eric Garcetti of Los Angeles, Bill De Blasio of New York, Mitch Landrieu of New Orleans and Pete Buttigieg of South Bend, Indiana — have emerged as rising stars of the Democratic Party at a time when Republicans control the White House, both houses of Congress, the governorships of 33 states and about 1,000 more state legislative seats than Democrats across the country.

Dysfunction in Washington, punctuated by the federal government shutdown, highlights why voters may look outside the usual places for future leadership, said Andy Ginther, the mayor of Columbus, Ohio.

"If you had a mayor in the White House, you wouldn’t be staring at a government shutdown," Ginther said Friday morning, just hours before President Donald Trump and congressional leaders failed to pass a stopgap spending bill. "They want a leader who can get things done, who isn't as worried about ideological purity. ... There's not a Democratic or Republican way to plow the streets or pick up the trash or to form public-private partnerships."

Centers of resistance and governance

The list of mayors who have competed for the presidency is short and relatively ignominious: Grover Cleveland of Buffalo is the only president who ran a decent-sized city first, and he was governor of New York in between. Only a handful have ever tried to jump from a mayoralty directly to the presidency, and they typically don't get very far. When Rudy Giuliani ran for president in 2008, his most recent government job was mayor of New York. He dropped out of the GOP primary after a poor showing in Florida.

But with Democrats down or out at other levels of government, cities have become both centers of the resistance to Republican rule and proving grounds for progressives to show they can govern effectively.

"Whether Washington, D.C., is making people angry or just disillusioned, it is providing cities an opportunity to help channel the emotions for a more productive focus," said Sam Liccardo, the mayor of San Jose, California. "There’s a pent-up demand to get involved and to make a difference. What has been happening has exacerbated a desire by many in our community to show Trump and Congress that we’ve got a better way at building a civil society."

This new reality has made mayors a hotter commodity in Democratic politics.

The leader of the pack

Garcetti has been on the front lines of Democratic mayors' efforts to resist Trump. At a time when the administration is trying to crack down on "sanctuary cities," Garcetti ordered municipal employees not to cooperate with the federal government unless legally required to do so. When Trump said he would pull out of the Paris climate agreement, Garcetti insisted that his city would adhere to its tenets.

That's endeared the Los Angeles executive, a Navy Reserve veteran who is both Hispanic and Jewish, to liberal activists and donors inside and outside his home city and state. While other mayors have been coy about their intentions, Garcetti has done little to dispel the notion that he's angling for the White House.

Mayor Eric Garcetti marked International Walk to School Day by walking with families to a local elementary school campus on Oct. 4, 2017. Office of Mayor Garcetti

"He’s not rejecting it out of hand, for damn sure, and he’s serious about thinking about it and he’s serious about doing some traveling" to promote economic development, innovation and Democratic candidates, said Bill Carrick, a Garcetti consultant who ran the 1988 presidential campaign of Dick Gephardt, then a Missouri congressman.

Carrick likened Garcetti's political skills to those of two other Democrats, former Presidents Bill Clinton and Barack Obama.

"He can talk to people one-on-one and be very effective at doing that," Carrick said. "He can do speeches with large audiences. He can do a living room with your classic Iowa or New Hampshire context with 20 people."

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That will be one of the tests for Garcetti, who has to convince Democrats that a left coast mayor who fought Trump on the environment and immigration is the right person to win in the swing states that cost them the presidency in 2016.

The millennial pragmatist

In a speech to Utah Democrats on Saturday night, Buttigieg, the South Bend mayor, criticized Trump for not having visited American troops in Afghanistan during his first year in office and compared his own past work to that of the Trump family.

"When Donald Trump and his sons were working on Season 7 of Celebrity Apprentice, I was driving and guarding convoys outside the wire in Afghanistan," Buttigieg said.

It might seem odd for the mayor of a small Indiana city to tackle the president on national security issues, but the 36-year-old Harvard graduate and Rhodes scholar has some standing on the conflict: He deployed to Afghanistan as a Navy Reserve intelligence officer.

Pete Buttigieg, the mayor of South Bend, Indiana, speaks at the Democratic National Committee Winter Meeting in Atlanta on Feb. 25, 2017. Alex Sanz / AP fil

"There’s been a need for mission clarity for some time and I think a realistic account of what we’re trying to achieve there," he said in a recent interview with NBC News. "I think we do have reason to be involved in ways that make sure that it’s not a source of terror threats to the U.S. And I think we continue to have an obligation to support the growth of a functioning state there. At a certain point we’ve got to have a certain realism about what we’re doing there and a framework that decides how serious we are about regional security."

Buttigieg, who recently announced his engagement to his boyfriend, raised his profile last year with a failed bid for the Democratic National Committee chairmanship. But the challenge of building a war chest and national name recognition would be immense for the mayor of a city of only about 100,000 people.

That said, his region is the just the kind of place where Democrats need to make a resurgence to win the presidency: South Bend is majority white but racially and ethnically diverse — and it's wrapped inside St. Joseph County, a prototypical midwestern swing area where Trump won by two-tenths of a percentage point in 2016.

Buttigieg's peers say he's a different kind of Democrat — progressive, but not showy about it.

"Mayor Pete is just one of the most innovative, results-oriented, reform-minded people out there," said Ginther, the Columbus mayor. "He is a guy who is driven by solving problems. You're not going to see a whole lot of ideological rhetoric or purity out of him."

The liberal lion

By contrast, de Blasio, the recently re-elected mayor of New York, wears his progressive values on his sleeve.

As the chief of America’s largest city, de Blasio has introduced universal pre-kindergarten and seen crime under his watch fall to historically low levels, while also phasing out the use of controversial policing methods like stop-and-frisk. Meanwhile, the city’s economy continues to soar, even as the mayor has pushed for higher taxes to fund some of his initiatives.

Mayor Bill de Blasio holds a press conference on the streets in the Greenpoint section of Brooklyn to applaud the decision from the New York Court of Appeals to uphold the Water Board's issuance of credits to homeowners on Dec. 20, 2017. Erik Pendzich / Rex Features via AP Images

He’s also emerged as a prominent figure within the Trump resistance, speaking out frequently against the president on a litany of issues, including his tax reform package and his immigration crackdowns. In September, de Blasio ripped Trump as “profoundly racist” and dubbed him “a hateful, negative person.”

Those kinds of comments, as well as his record, have helped him emerge as one of a handful of politicians who could reasonably be labeled a spokesperson for the Democratic Party’s liberal wing.

And that de Blasio seems to harbor bigger political ambitions isn’t a very well-kept secret. He traveled to Iowa in December, giving heartland voters in the first-in-the-nation’s caucus state a taste of his vision for the country. “We are at the beginning of a progressive era,” he said, adding that he was not running for president. Weeks later, at the inauguration for his second term, he was sworn in by Vermont Sen. Bernie Sanders, the progressive hero who took a worthy stab at knocking off Hillary Clinton in the 2016 Democratic race.

That kind of unabashed leftward emphasis could help in a presidential primary, when candidates tend to cater to the fringes of their parties. And de Blasio certainly has a lot of fans among his fellow City Hall chiefs across the U.S., although many wonder if Democratic voters nationwide would go for such an obvious progressive — and another New Yorker.

“Bill de Blasio has done a remarkable job building on the momentum in New York, and with public safety,” said Mike Rawlings, the mayor of Dallas. “Obviously, though, he represents the more progressive arm of the Democratic Party.”

“So, the question is, does it play in Peoria?” he added, using an old political adage.

The Southern Democrat

In 2010, New Orleans, just five years removed from Hurricane Katrina, was broke and grappling with corruption and a slew of other aftereffects of the devastating storm.

Then, Mitch Landrieu took office.

New Orleans Mayor Mitch Landrieu speaks in Washington on race in America and his decision to take down Confederate monuments in his city on June 16, 2017. Jacquelyn Martin / AP file

Eight years later, the Big Easy has seen a substantial drop in unemployment, including a decline in black unemployment by nearly 20 percent, a drastic uptick in the city’s credit rating and a return to the robust tourism revenues that the area depends on.

The turnaround has elevated the profile of the 57-year-old scion of a well-known Louisiana political family, leading a growing class of fellow mayors that have many wondering whether a midsize-city CEO from the South could, in fact, represent the future of the Democratic Party.

It has been Landrieu's attitudes on race and history, however, that have, perhaps, garnered him the most attention in that conversation.

Landrieu, the first white mayor of New Orleans since his father, Moon Landrieu, held the office in 1970s, earned plaudits for taking on the Confederacy's legacy in his city. Last year, after his City Hall took down four Confederate monuments, Landrieu delivered a passionate speech outlining why doing so was important.

"We need to change," he said in May. "And we need to change now. No more waiting. This is not just about statues, this is about our attitudes and behavior as well. If we take these statues down and don’t change to become a more open and inclusive society, this would have all been in vain."

His comments were a clairvoyant contrast to those offered by Trump two months later, after violence broke out in Charlottesville, Virginia, during race-fueled riots.

A spokesman for Landrieu’s office told NBC News the mayor had “no intentions" of running for president.