It’s the question both 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 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 will have to consider in the coming months: Is the 2020 Democratic primary big enough for both of us?

Even before the midterm elections, allies to both progressive senators are trying to figure out if there's a way they can both run in the primary and, if so, how they can best stand out from one another.

Allies on both sides acknowledge the potential problems with two senators so ideologically similar running against one another.

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“They could cancel each other out,” said one Sanders ally who advised the Vermont senator during his 2016 presidential campaign. “Both of them clearly want to run, but both of them together in a primary? It is kind of redundant.”

Associates expect Sanders and Warren to sit down and discuss the 2020 race sometime after the midterms. The two had a similar conversation ahead of the 2016 election, when Sanders told his counterpart from Massachusetts that one of them should run for president.

“It’s tricky,” the Sanders ally added when describing the conundrum ahead. “They’re both very similar. She has everything Bernie has, and he’s very well aware of that.”

An aide to Sanders did not respond to a request for comment. A spokesperson for Warren declined to comment.

Supporters to both senators say that Sanders and Warren have a solid friendship and working relationship, but strategists predict tensions will grow increasingly palpable as 2020 inches closer.

“Warren and Sanders watch each other as much as the Yankees and Red Sox check up on each other in the American League East,” said Brad Bannon, a Democratic strategist.

He predicted one of the two will likely fall out of the race if the primary devolves into a battle between the left and center of the party.

“It will be the biggest rivalry because only one of them will survive long enough to challenge 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 for the nomination,” he said.

Each senator is seeking to highlight their strengths as the shadow primary turns into something more real.

Sanders has had an organization in place since 2016, and the loyalty his supporters have for him is second to none. He also can take credit for pushing forward "Medicare for all," a single-payer health-care plan that now has the support of many Democrats, including Warren.

Supporters of Sanders say he can appeal to both Democrats and independents given the fact that he serves as an independent. They also say Sanders has earned the right to run again after coming so close to defeating 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 in 2016.

“He has definitely reshaped the political landscape and he feels like this is his,” the Sanders ally said of 2020.

Warren may have more support than Sanders within the Democratic establishment, where many still see Sanders as an imposter who uses the party to suit his own needs.

In the "Me Too" era, her supporters say that she will also appeal to women and their desire to shatter the glass ceiling.

“The most important difference between Sanders and Warren is gender,” Bannon said. “Female Democrats are kicking male butt in the primaries this year. Most of the people who attend Democratic caucuses and vote in the party primaries in 2020 will be women. The 'Me Too' movement, Donald Trump’s behavior towards women and the threat to legal abortion have galvanized women in the Democratic Party. This will give an edge to Warren over Sanders.”

Last week, a CNN tracker of “monthly power rankings” of would-be 2020 Democratic presidential candidates ranked Warren in the top spot, adding, “It’s increasingly clear that Warren fits the political moment better than most and can unite the different factions of the Democratic Party.”

At the same time, a Politico–Morning Consult poll out last month showed 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 trailing Sanders 44 to 32 percent. The same poll shows that Trump trails Warren 34 percent to 30 percent. The poll showed 36 percent of voters were undecided.

Warren and Sanders are highlighting differences between one another.

Sanders is a self-described democratic socialist. Warren, who has railed against corporate greed and corruption, says that she believes in capitalism.

“I believe in markets right down to my toes,” she said on MSNBC in July.

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It’s a message that could appeal to Democratic voters worried that Sanders isn’t really a Democrat or is too far to the left. But vouching for your capitalist credentials, at the same time, might not be the best strategy for attracting younger voters — a strength of Sanders’s in 2016.

A Gallup survey released last month showed that 45 percent of Americans between the ages of 18 and 29 have a positive view of capitalism, down from 57 percent in 2016, when Sanders railed against it.

Can Sanders pull off a sequel to his stunning success in 2016?

Cal Jillson, a professor of political science at Southern Methodist University, cautioned that while Sanders might have “a natural advantage” because of his first campaign, “it’s tough to capture lightning in a bottle twice.”

Jillson said Sanders would have to talk about his policies “in more nuanced terms” his second time, since he’ll no longer just be the insurgent candidate.

“You’ve got to be a lot more substantive,” he said. “You have to be able to talk in paragraph form and not just bumper sticker slogans."