The first, overt intra-party salvos of the 2020 Democratic primary have been launched, and history will show that they came over the membership of a committee in the United States Senate.

Over the past day, two potential candidates for president have put out statements demanding that Sen. Joe Manchin (D-WV), a conservative pro-coal Democrat, not be given the position of ranking member of the Senate Energy and Natural Resources Committee.

The statements, issued from Governor Jay Inslee (D-WA) and Democratic financier Tom Steyer, have elevated an otherwise arcane process for filling out committee hierarchy and, in doing so, conspicuously set a benchmark for other potential presidential candidates—including several of Manchin’s Senate Democratic colleagues.

“Look, Joe Manchin has been a champion for affordable health care for every American. He's been a leader on issues you and I care deeply about. But on climate, he's simply wrong,” Inslee wrote in an email circulated to supporters on Tuesday evening.

The next morning, Steyer told The Daily Beast that he shared those concerns.

"Every American has the right to clean air and clean water, and it’s time for those in Washington, D.C. to stop playing politics and to take real action on climate,” said Steyer. “Democrats must offer a bold, positive path forward— but Senator Manchin does not offer that vision and should not be the Democratic leader on the Senate Energy and Natural Resources Committee. Senate Democrats owe it to their constituents to tell the truth, acknowledge the urgent climate crisis we’re in, and do what’s right—instead of what’s politically expedient for them."

Rare are the cases where the most powerful position of the minority party on a Senate committee becomes fodder for a national political litmus test. But such are the fears that Manchin’s environmental policies have engendered.

The senator famously shot a copy of cap-and-trade legislation with a shotgun in a TV ad for his first run for the Senate in 2012. He recently voted for the confirmation of David Bernhardt, a lobbyist for the oil-and-gas and agribusiness industries, to be second-in-command at the Department of the Interior. And the influence of the coal industry in his state has prompted concern that he would stand in the way of progressive-minded reform should Democrats ever take back the majority in the Senate and he end up as chair of the energy committee, which will play a potentially vital role in working on climate change legislation.

Manchin’s office declined to comment for this piece. But the 2020 implications don’t end there.

One way Manchin could be boxed out of the ranking member spot on the energy committee would be if Sen. Bernie Sanders (I-VT) decides he wanted it instead. According to the Democratic Party’s seniority rules, Sanders is in line for the post before Manchin. And the Vermonter has made advocacy for environmental reforms a key component of his political appeal.

And yet, the problem persists.

That’s because Sanders, despite his speeches about the perils of climate change—including a town hall on Monday night to draw further attention to the crisis—has appeared inclined to remain ranking member on the budget committee rather than make the switch.

Some of those who have worked with Sanders say he is hesitant to do so because of a dual set of concerns: the first being that the budget committee provides a platform for him to emphasize numerous issues (health care, social security, and so on) rather than be associated with just one; the second being that it could be difficult to juggle the energy committee’s demands with a presidential run, should he choose to launch one.

“He takes his responsibility in the United States Senate and his service to the people of Vermont very, very seriously,” Mark Longabaugh, a senior adviser on the 2016 campaign told The Daily Beast. “And in the 15-16 campaign, if you read [former campaign manager] Jeff Weaver’s book, one of the things that Jeff talks about was that throughout 2015, Bernie Sanders was a full-time senator and we were basically running a campaign when the Senate was out and on weekends.”

“I cannot imagine that were he to run again, that he would in any way abandon his Senate responsibilities which he takes seriously,” Longabaugh continued, acknowledging that he doesn’t know specifics about the committee decision-making process now.

Senate aides studiously refused to comment on what type of private pressures are being put on Manchin, Sanders or others, noting that party leadership first has to determine how many seats each committee would be given before engaging in any discussions about committee leadership. But the person who has come under the most scrutiny to find a resolution has been Senate Minority Leader Chuck Schumer (D-NY).

“There are only two politically salient facts,” Lukas Ross, senior policy analyst at Friends of the Earth, told The Daily Beast. “Joe Manchin is categorically unacceptable. The second is that Chuck Schumer can absolutely fix this.”

On Monday, the Brooklyn chapter of progressive advocacy group Indivisible held a protest at Schumer’s Manhattan office with the climate organization Sunrise Movement to demand that Manchin not be allowed to serve in the post.

“[Schumer]'s the minority leader. If he made it a priority to recruit someone better to fill this role, we think he could figure it out!” Indivisible BK co-president Liat Olenick said when asked who they found at fault for Manchin’s possible ascension.

Schumer’s office declined to comment for this piece. But as he and others try to find a resolution, they are being forced to juggle numerous political variables. Chief among them is how much pressure can be placed on Manchin, who just won re-election but has also been considered by the Trump administration as a possible Cabinet pick. The second is how many demands can be imposed on caucus members who are contemplating a run for president, Sanders among them.

Schumer may very well find a way to resolve the potential problem that doesn’t involve placing pressure on Manchin or Sanders but not without some serious senatorial musical chairs.

Currently, Sens. Ron Wyden (D-OR), Debbie Stabenow (D-MI), and Maria Cantwell (D-WA) also serve on the energy committee, and all outrank Manchin. But Wyden and Stabenow are also ranking members of the finance and agriculture committees, respectively, and they’d have to give up those titles if they wanted to hold the ranking position on energy.

Senate aides said neither Wyden nor Stabenow is expected to trade their current posts for what is considered to be a less prestigious assignment.

Which leaves Cantwell.

But the Washington senator is in line to become the ranking member of the Commerce Committee, a key committee for several of the major industries in her state. She would have to be convinced to forgo that position to stay on energy in order to block Manchin. And that’s a proposition that Inslee’s office declined to place on the fellow Washingtonian.

“Ensuring Senator Manchin doesn't become Democrats' leader on energy policy is not Senator Cantwell's responsibility,” Inslee spokesperson Jamal Raad told The Daily Beast. “She has been an incredible advocate for Washington State and the environment in her current role, and would have important opportunities to advance progressive policies for both on Commerce.”

The presumption among Senate aides is that the process will end up with Manchin assuming the role of ranking member absent some interceding event. “It seems like it is a done deal,” said one Senate aide. “Most people are resigned to Manchin taking the helm.”

And Manchin, for his part, seems to be subtly trying to silence his critics in the lead-up to any resolution. On Wednesday, the West Virginia Democrat voted against final confirmation of Bernard McNamee’s nomination for the Federal Energy Regulatory Commission (FERC). McNamee, who passed by a 50-49 vote, was widely criticized as an ally of the coal industry and a skeptic of renewable energy. When his nomination first came up before the energy committee in November, Manchin had been the lone Democrat to offer his support.

“After viewing video footage, which I had not previously seen, where Bernard McNamee outright denies the impact that humans are having on our climate, I can no longer support his nomination to be a FERC Commissioner,” Manchin said in a statement. “Climate change is real, humans have made a significant impact, and we have the responsibility and capability to address it urgently. I also continue to believe that science and technology will be critical to ensuring that the United States continues towards a clean energy economy, but we can’t make progress if our public officials deny that a problem even exists.”