Elizabeth Warren and Bernie Sanders Have a Problem: Each Other They’ve abided by a de facto nonaggression pact. But to win the Democratic nomination, one must prevail over the other by consolidating the left.

Elizabeth Warren and Bernie Sanders Have a Problem: Each Other 

They’ve abided by a de facto nonaggression pact. But to win the Democratic nomination, one must prevail over the other by consolidating the left.

By Jonathan MartinUpdated 

FAIRFIELD, Iowa — Diane Chojnowski and Denyce Rusch were among the Iowans who braved light snowfall and temperatures in the teens to see Senator Bernie Sanders on Sunday afternoon, a few hours before Senator Elizabeth Warren was also due in this liberal pillar of eastern Iowa.

But after Ms. Chojnowski and Ms. Rusch praised Mr. Sanders, they turned to a predicament far more bothersome than the winter weather: choosing between the two progressive candidates.

“You worry about Bernie and Elizabeth splitting the progressive vote because between the two of them they’ve got a huge bloc,” said Ms. Chojnowski, who initially considered Ms. Warren but has come back to Mr. Sanders because, as she put it, “he’s the thought leader.”

She is not the only liberal voter alarmed.

Since the presidential primary race began, the two progressive senators — who have been friends since Ms. Warren was elected to the Senate in 2012 — have abided by a de facto nonaggression pact, rarely criticizing one another and frequently acting as something of a populist tag team on the debate stage. And as Pete Buttigieg has risen in the polls and Joseph R. Biden Jr. has proved durable, Mr. Sanders and Ms. Warren have been happy to demonstrate their left-wing bona fides by contrasting themselves with the more moderate contenders.

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Yet with Mr. Sanders enjoying a revival after his heart attack in October and Ms. Warren receding from her summer surge but wielding a formidable political organization in the first nominating states, it’s increasingly clear that their biggest obstacle to winning the Democratic nomination is each other.

In Iowa and nationwide, they are the leading second-choice pick of the other’s supporters, a vivid illustration of the promise and the peril that progressives face going into 2020: After decades of losing intraparty battles, this race may represent their best chance to seize control from establishment-aligned Democrats, yet that is unlikely to happen so long as Ms. Warren and Mr. Sanders are blocking each other from consolidating the left.

For center-left Democrats, that’s exactly their hope — that the two progressives divide votes in so many contests that neither is able to capture the nomination. Moderates in the party fear that if Ms. Warren or Mr. Sanders pull away — or if they ultimately join forces — the ticket would unnerve independent voters and go down in defeat against President Trump.

Interviews with aides from both camps — who spoke on the condition they not be named because they warn their own surrogates not to criticize the other — produce a common refrain. The two candidates are loath to attack each other because they fear negativity would merely antagonize the other’s supporters. The only way to eventually poach the other’s voters, each campaign believes, is by winning considerably more votes in the first caucuses and primaries.

Liberal leaders, acknowledging the mixed blessing of having two well-funded, well-organized progressive Democrats dividing endorsements and poised to compete deep into the primary calendar, are now beginning discussions about how best to avert a collision that could tip the nomination to a more centrist candidate.

At informal Washington dinners, on the floor of the House and on activist-filled conference calls, left-leaning officials are deliberating about how to forge an eventual alliance between Mr. Sanders, of Vermont, and Ms. Warren, of Massachusetts. Some are urging them to form a unity ticket, others want each to stay in the race through the primary season to amass a combined “progressive majority” of delegates, and nearly every liberal leader is hoping the two septuagenarian senators and their supporters avoid criticizing each other and dividing the movement.

“It can’t be, One candidate is the true god or goddess and the others are just shills,” said Representative Pramila Jayapal of Washington, who backed Mr. Sanders in 2016 but has not yet endorsed anyone in this race. “It really has to be, We’re trying to strengthen them both.”

On Saturday, Robert Reich, a former secretary of labor, sent an email to members of the progressive group Democracy for America warning that if supporters of the two candidates “wage war on each other” that it would “take both of them down.”

Former Senator Harry Reid of Nevada, one of the few prominent Democrats who commands the respect of both Mr. Sanders and Ms. Warren, said he was ready to step in if needed.”