If these seem like distinctions without much meaning to critics — since even the least ambitious of these plans would require liberal Democratic majorities in Congress to pass — they’re all part of the contest between Sanders and Warren to be recognized in the Democratic primary as the lead champion for progressives. At the same time, the war over white papers has terrified moderate Democrats, who worry that a race to the left will damage the party’s chances of defeating President Donald Trump — even as it electrifies the base.

"This is exactly the primary we should be having,” said Alex Lawson, executive director of the advocacy group Social Security Works. “When candidates compete to release the boldest policies, everyone wins — except the billionaires.”

But the escalating ambition and price tag of the proposals has also been turned into ammunition for Sanders and Warren’s more moderate opponents, such as former Vice President Joe Biden, Sen. Amy Klobuchar, and South Bend, Ind., Mayor Pete Buttigieg.

“When candidates compete to release the boldest policies, everyone wins — except the billionaires.” Alex Lawson, executive director of Social Security Works

“The stakes of defeating Donald Trump and the assaults on our values he commits daily are too great for our primary to devolve into who can sacrifice our policy advantages in a general election the fastest,” said Biden spokesman Andrew Bates.

Warren and Sanders regularly dismiss such criticism and argue that the dearth of big ideas is what caused the party to lose the White House to Trump in the first place.

From criminal justice to campaign finance to foreign affairs, the policy skirmishes between Sanders and Warren have touched on nearly every big topic in the primary and broadened the debate among Democrats. For instance, along with Sanders, several candidates endorsed the idea of a wealth tax or said they were open to it after Warren rolled out hers.

Sanders and Warren have largely avoided direct conflict on the campaign trail, and neither campaign provided a comment for this story. But the policy feuds speak to growing tension between the two candidates below the surface.