The race for the Democratic presidential nomination is a wide-open contest with no clear front-runner for the first time in years.

While former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE, Rep. Beto O'Rourke Beto O'RourkeJimmy Carter says his son smoked pot with Willie Nelson on White House roof O'Rourke endorses Kennedy for Senate: 'A champion for the values we're most proud of' 2020 Democrats do convention Zoom call MORE (Texas), and Sens. Bernie Sanders Bernie SandersOutrage erupts over Breonna Taylor grand jury ruling Dimon: Wealth tax 'almost impossible to do' Grand jury charges no officers in Breonna Taylor death MORE (I-Vt.) and Elizabeth Warren Elizabeth WarrenDimon: Wealth tax 'almost impossible to do' CNN's Don Lemon: 'Blow up the entire system' remark taken out of context Democrats shoot down talk of expanding Supreme Court MORE (Mass.) have drawn a lot of attention, Democrats say the 2020 race is anybody’s game.

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It’s a race that is expected to attract dozens of candidates, from big city mayors such as Los Angeles’s Eric Garcetti to bright new political stars such as former Tallahassee Mayor Andrew Gillum and Stacey Abrams, who narrowly lost her bid to win Georgia’s governorship.

Democratic House lawmakers, including Reps. Eric Swalwell Eric Michael SwalwellSwalwell calls for creation of presidential crimes commission to investigate Trump when he leaves office 'This already exists': Democrats seize on potential Trump executive order on preexisting conditions Swalwell: Barr has taken Michael Cohen's job as Trump's fixer MORE (Calif.) and John Delaney John DelaneyCoronavirus Report: The Hill's Steve Clemons interviews Rep. Rodney Davis Eurasia Group founder Ian Bremmer says Trump right on China but wrong on WHO; CDC issues new guidance for large gatherings The Hill's Coronavirus Report: Kansas City Mayor Quinton Lucas says country needs to rethink what 'policing' means; US cases surpass 2 million with no end to pandemic in sight MORE (Md.) — who has already announced his candidacy — are also in the mix.

"I wouldn't be surprised if it is a dark horse candidate — somebody we haven't even thought about —who ends up getting the nomination," said Democratic strategist Maria Cardona.

Here are five dark horse contenders who could win it. And a warning: There may be others.

Amy Klobuchar Amy KlobucharSocial media platforms put muscle into National Voter Registration Day Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE

The Minnesota senator has long been on lists of 2020 contenders, but always seems to be in the second breath behind other female colleagues in the Senate — including Warren, Kamala Harris Kamala HarrisHarris faces pivotal moment with Supreme Court battle Nearly 40 Democratic senators call for climate change questions in debates Joe Biden has long forgotten North Carolina: Today's visit is too late MORE (Calif.) and Kirsten Gillibrand Kirsten GillibrandSunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Suburban moms are going to decide the 2020 election Jon Stewart urges Congress to help veterans exposed to burn pits MORE (N.Y.).

But Klobuchar shouldn’t be underestimated.

A new poll of Iowa voters showed she’s in the mix in the neighboring state, and she won national attention during the confirmation hearings for Supreme Court Justice Brett Kavanaugh Brett Michael KavanaughHarris faces pivotal moment with Supreme Court battle Poll: 59 percent think president elected in November should name next Supreme Court justice Feinstein 'surprised and taken aback' by suggestion she's not up for Supreme Court fight MORE.

“She showed a lot of grit,” said Democratic strategist Patti Solis Doyle, who served as campaign manager during Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE’s 2008 presidential bid.

In a year when women have dominated in politics across the board, Solis Doyle and others say Klobuchar should be a top contender.

“There is no way that the Democratic Party will have two white men on the ticket in 2020 so each female candidate thinking about running should be given a close look,” she said.

One key advantage for Klobuchar that could help her in comparison to colleagues Harris and Warren is that she hails from the Midwest, an area Democrats must win back from President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE in 2020.

Mitch Landrieu

The former New Orleans mayor caught the eye of Democrats after he delivered a powerful speech last year on the removal of Confederate monuments from his city.

The speech went viral, leaving some wondering if a red-state Democrat like Landrieu could take the party by storm.

Landrieu has kept a relatively low profile since leaving his mayoral office and Democrats who have spoken to him say he’s considering his options.

Some Democrats see him as a candidate who could stand out in the crowd even as the party increasingly tacks left.

“Before Obama, the two biggest Democratic dark horses have been Democrats holding local office, Bill Clinton William (Bill) Jefferson ClintonEpstein podcast host says he affiliated with elites from 'both sides of the aisle' Ruth Bader Ginsburg lies in repose at Supreme Court Business groups start gaming out a Biden administration MORE and Jimmy Carter,” said Democratic strategist Brad Bannon. “The South is becoming ever so slowly more friendly to Democrats. Landrieu could capitalize on that trend.”

Steve Bullock

Who can beat Trump? Maybe someone who won reelection handily in a state the president won solidly.

Bullock, the governor of Montana, can tout his experience working with a legislative body that is largely Republican while presiding over a state economy with record-low unemployment and growth in industries including manufacturing.

He’s shown all the signs that he’s prepared to launch a presidential bid, traveling to Iowa several times this year and quietly making the rounds on the fundraising circuit.

He still lacks name recognition and that’s what’s hurting him now, one major Democratic donor said.

“I’ll talk about him and the overwhelming reaction is ‘Who?’ If he fixes that, I think a lot of people will give him a good look,” the donor said.

Sherrod Brown Sherrod Campbell BrownHarris faces pivotal moment with Supreme Court battle Remote work poses state tax challenges Senate Democrats release report alleging Trump admin undermined fair housing policies MORE

Democrats have been desperately hunting to find someone who could appeal to centrists and progressives alike and some see Brown, an Ohio senator who just won reelection in a state carried by Trump, as the solution.

If Democrats can win back Wisconsin, Pennsylvania and Michigan, they’d likely win the White House. Brown, a liberal on social policies who can sound like Trump on trade, is seen as someone who could appeal to voters in those states as well as his home state of Ohio.

Brown has sounded more like a candidate testing a national message his his reelection victory, and it’s a message that has been geared to working-class Democrats.

“Sherrod Brown has been a champion for America’s workers his entire career and America is just now catching on,” said Seth Bringman, a Democratic strategist who hails from Ohio. “He doesn’t cede one inch on progressive values and yet he wins Ohio handily because he is a fighter for struggling families at his very core.”

Jay Inslee

The Washington governor’s profile has been on the rise in recent years and he has been drawing eyes to his policies and politics with appearances on national television.

Most notably, he garnered attention after his state’s legal victories in blocking Trump’s travel ban last year. “He got thumped,” Inslee told CNN at the time, hitting back at Trump.

More recently, he has sought to highlight climate change, an issue that will inevitably appeal to the base.

In a recent interview with Rolling Stone, he said it was “absolutely imperative” for the Democratic Party to have a nominee who will champion the issue. “I believe it’s a potentially winning issue to run on,” he told the magazine. “And we need a candidate who will do that.”