The battle for control of the Democratic party continues where it left off in 2016. In place of the relatively moderate Hillary Clinton, this year we have moderate front runner Joe Biden. And in place of the far left Bernie Sanders we have Bernie Sanders and Elizabeth Warren. And therin lies the problem for the Democratic Socialists in the party. Their vote is split between two candidates who have enough money to go the distance in the primaries.

Thus far, Warren and Sanders have mostly played nice with one another but that will probably have to end at some point if the far left wants a real chance at rivaling Biden. But there’s an obvious danger for the left if their candidates go on the attack against one another. They could both be damaged in the effort, allowing Biden to consolidate his lead relatively unscathed. But some within the party see a possible solution: Have the two far left candidates team up on a single ticket:

Representative Ro Khanna of California, a co-chairman of Mr. Sanders’s campaign, said the solution would be to create a Sanders-Warren ticket.

“The two of them could usher in a progressive era for the next decade,” said Mr. Khanna, likening such a maneuver to what Bill Clinton did by tapping another young and fairly moderate Southerner, Al Gore, as his running mate in 1992. “They doubled down on a bet for a centrist vision of the party. This would be a bet on a progressive vision for the party.”

Another Sanders supporter, Representative Ilhan Omar of Minnesota, was equally effusive. “I think that would just be the dream of all progressives,” she said. “When you’re going into a battlefield, you want your best players to be on the field starting. And they are our best.”

This may be the dream of some socialists but it’s an open question whether the Bernie Bros would accept Warren and withhold fire. The sticking point might be her recent decision to take a step back from Medicare for All.

To really appreciate this you have to consider the history of Warren’s positioning on this issue. Warren adopted Sanders’ Medicare for All plan wholesale several months ago when she was trying to run to the left of the field. That seemed to work for her. She went up in the polls and raised a lot of money. But then came the stories suggesting Democratic donors were very worried about Medicare for All and what it would do to Democrats’ chances of winning the White House. In short, what works in the primary doesn’t always work in the general election.

Warren also had another problem. She had used all kinds of fantasy math to claim that her M4A proposal wouldn’t raise taxes on the middle class. That claim was not remotely convincing to anyone who looked at the plan but it appeared to be Warren’s first attempt to make Sanders’ health plan politically viable in the general election. But as the negative stories about her plan began to pile up, Warren had a sudden change of heart. In mid-November she introduced a new transition plan which would put off M4A for at least three years.

As a lone candidate trying to remain viable in the general election, this move made sense. It allowed Warren to say the scary expensive parts of M4A were down the road and would all be worked out later. But as a possible partner on a progressive unity ticket with Sanders, her change of heart on M4A was a betrayal of a core issue. Would the Bernie Bros really be willing to play nice with someone who adopted and then abandoned M4A?

Until she unveiled her own, more gradual implementation plan — after weeks of saying “I’m with Bernie” on Medicare for all — Ms. Warren had carefully guarded her left flank to avoid handing Mr. Sanders any fodder.

Now, Mr. Sanders’s aides say Ms. Warren’s shift has signaled to progressive voters that she is malleable on what they consider a fundamental values issue. Her pivot on health care, along with the support she enjoys from a handful of billionaires, represents the best opportunity to diminish liberal enthusiasm for Ms. Warren, say Sanders supporters.

So there you have it. Some far left progressives are dreaming their two champions will combine forces to take out Biden, but at least some on the left consider Warren a compromised poser. The pressure for the two camps to battle it out is building and may put an end to the de facto truce we’ve seen between the two camps so far. So stock up on popcorn, this is about to get interesting.