The 2018 election results aren’t official yet, but minds are already turning to Colorado’s next big electoral contest: U.S. Sen. Cory Gardner’s 2020 re-election bid.

Given the mood of Colorado’s electorate in 2018, the Republican’s chances appear at first blush to be grave. And Gardner’s critics piled on again after the chairman of the National Republican Senatorial Committee defended Republicans’ objections over vote counting in Florida on “Meet the Press” on Sunday. However, a lot can happen between now and Election Day 2020, including a Democratic primary election that will pick Gardner’s opponent.

There is no shortage of potential challengers, political watchers said this week. However, four names are on top of most lists: Colorado House Speaker Crisanta Duran, former state Sen. and gubernatorial candidate Mike Johnston, U.S. Rep. Ed Perlmutter and Gov. John Hickenlooper.

“The field is very much in flux, and there are a lot of conversations to be had,” said Craig Hughes, a Democratic campaign strategist who helped U.S. Sen. Michael Bennet win his first election in 2010. Hughes also ran Johnston’s gubernatorial bid.

The stakes are high for whichever Democrat emerges from the primary. Gardner is one of only two Republican incumbents in Senate races that Democrats will likely target as pickups. The other is U.S. Sen. Susan Collins of Maine. That means, Hughes said, the general election will be “incredibly expensive, competitive and negative.”

Let’s take a look at what each of the potential top contenders would bring to the table:

State House Speaker Crisanta Duran

The 2018 election saw a historic number of women and people of color elected to Congress. And if Duran, who was Colorado’s first Latina speaker of the House, could capture some of that momentum, it could easily propel her candidacy forward. Duran has also been a forceful critic of President Donald Trump — especially on his immigration policies.

“Crisanta would be a formidable opponent for Gardner — she’s young and Latina, was extremely successful in the state Capitol, and represents a demographic he’s never been able to connect with,” said Micha Rosenoer, the executive director of Emerge Colorado, a political group that trains women to run for office.

Insiders suggested she could easily be considered the most progressive candidate of the bunch. And while that might get her through the primary, there is a question of how much appeal and name recognition she has outside of Denver, her home base.

Duran’s interest in challenging Gardner is well known in Democratic circles. However, publicly Duran is more cryptic.

“I’m currently focused on helping Governor-elect Jared Polis with his transition team and finishing up my term as Speaker,” she said in a statement. “I’m proud of the issues we’ve been able to problem solve for our state. As for my next steps, I am interested in being in a role where I can be most effective and build upon the work I’ve done but haven’t made a final decision about what that is.”

Former state Sen. Mike Johnston

Johnston came in third in the Democratic gubernatorial primary. But his campaign, which focused intensely on unaffiliated voters and took him to all 64 counties, gives him statewide name recognition among the party’s base. The former Denver lawmaker is a native son of the Rocky Mountains, which lends him credibility with voters who live in the mountains and on the Western Slope.

“He’s the kind of candidate Republicans would prefer not to face,” said independent consultant Eric Sondermann. “His challenge is going to be the Democratic primary.”

Before running for governor, Johnston was perhaps best known for his work on education reform, including the state’s controversial teacher evaluation system. His work on those issues gave him access to a vast national network of wealthy donors who support his vision for public education. The out-of-state dollars would allow him to go toe to toe with Gardner. But it could spoil his chances in the primary, especially if the state’s teachers union, which targeted him in an attack ad during the 2018 primary, has anything to say about it.

Johnston acknowledged in an interview with The Denver Post that he’s considering a run.

“A lot of folks have reached out and asked me to consider running,” he said. “I share the belief that Cory is not representing the interests of the state. … (But) I haven’t made any decision.”

Johnston added that he’ll be discussing a possible campaign with his family during the Thanksgiving holiday.

U.S. Rep. Ed Perlmutter

Perlmutter, who represents the state’s 7th Congressional District, is among the state’s most popular Democratic leaders. And the Arvada lawmaker, known for his retail politics, likely would have a lock on Colorado’s most important swing county, Jefferson, which he has represented in Congress for more than a decade.

“There are a couple of giants in the Democratic Party that could shape this race, and Ed Perlmutter’s at the top of the list,” Hughes said.

Perlmutter has attempted a run for statewide office before. For about three months in 2017, he was the presumptive front-runner in Colorado’s gubernatorial race. However, he bowed out after colleague Rep. Jared Polis jumped into the race. At the time of his exit, Perlmutter said he didn’t have the “fire in belly” to run a statewide campaign. Will that change in the next two years? Will it matter that Gardner doesn’t have Polis’ millions to self-finance? Maybe.

Perlmutter declined to comment.

Gov. John Hickenlooper

Don’t be fooled by the trips to Iowa and New Hampshire, Democrats have been trying to convince themselves, Hickenlooper is going to challenge Gardner in 2020. The two-term centrist governor has the record, popularity and infrastructure to easily clear the primary field and take it straight to Gardner.

While the state’s politicos might have him pegged as the man for the job, does he want it?

“The top of the class is John Hickenlooper, but obviously he has his eyes set on something else,” Sondermann said. “The question is, if that something else doesn’t work out, would he look at the Senate as a consolation prize?”

While observers believe that Hickenlooper would easily capture the Democratic nomination, others are doubtful about his interest in facing off against Gardner.

“He’s an executive-branch guy,” said Ian Silverii, executive director of Progress Now Colorado, a progressive political nonprofit. “I don’t see him running for the U.S. Senate.”

Hickenlooper’s team declined to comment.

Race could be “a mosh pit”

“It’s going to be a crowded field,” Silverii said. “I won’t be surprised if it’s a mosh pit.”

Here are a few other possible candidates Democratic consultants and observers said they’re keeping their eye on as the primary begins in earnest early next year:

Stan Garnett, the former Boulder district attorney and one-time attorney general candidate, said last year on social media that he’d look closely at a 2020 run.

Trish Zornio, a Superior scientist, has already formed an exploratory campaign.

Cary Kennedy, the runner-up in the gubernatorial Democratic primary, has the statewide network to tap if she isn’t ready to get out of politics.

State Rep. Joe Salazar, a Thornton Democrat who is not returning to the statehouse next year, is a liberal firebrand with ambition.

John Walsh, the former U.S. attorney for Colorado, was appointed by then-President Barack Obama and now works with former U.S. Sen. and Interior Secretary Ken Salazar.

Update: This article has been updated to clarify that Joe Salazar is still a state representative until 2019.