Not exactly two peas in a pod. Photo: Bill Clark/CQ Roll Call

It’s no secret that Senators Bernie Sanders and Elizabeth Warren pull from the same base. They are Senate allies and friends, and have conspicuously refused to criticize each other on the 2020 presidential campaign trail. They are both scourges of Wall Street and inveterate critics of what some progressives love to call corporate Democrats, have close ties to the labor movement, and are calling for a pretty significant break from bipartisan foreign policy and national security conventions. So for voters trying to choose between these two New England progressives — and for other Democratic primary voters who may eventually be driven toward either or both of them — the differences between them are sometimes subtle and implicit rather than obvious and explicit.

Aside from the obvious difference in gender, and a relatively small but perhaps significant difference in age (both are over 70, but only Sanders would turn 80 in a first term as president), they have stylistic differences that affect the nature of the coalitions they are assembling for 2020. Bernie with his fiery, no-compromise approach famously does well among under-30 voters, and is doing better than he did in 2020 among nonwhite voters. Warren’s more cerebral, policy-heavy pitch is giving her a big following among college-educated voters. Sanders calls himself a democratic socialist, while Warren argues she is trying to save capitalism. Their campaign organizations reflect other differences in temperament: Warren is building a world-class, paid professional staff that has impressed political veterans in the early states, while Sanders’s campaign depends on volunteer heft, which no campaign does better.

But there is another difference in their approach to 2020 that is only apparent on the campaign trail to those who are watching closely, as explained by Jonathan Martin after some close scrutiny of Warren’s conduct on the stump:

When Senator Elizabeth Warren of Massachusetts addressed a few hundred donors last week at a fund-raiser for the Democratic National Committee, she called for “big, structural change” and hurled her familiar populist lightning bolts at the forces of concentrated wealth.

But Ms. Warren did not attend the event just to recite her stump speech. She had another, more tailored message for the Democratic check writers, state party leaders and committee members who were gathered at the elegant Fairmont San Francisco.

“Last year, I was running for re-election, but I didn’t hold back,” she said, reminding attendees that in the midterms she had helped more than 160 congressional candidates and nearly 20 hopefuls in governors’ races. “In fact, I raised or gave more than $11 million helping get Democrats elected up and down the ballot around the country” and “sent contributions to all 50 state parties, the national committees and the redistricting fight.”

Her point was easy to grasp: While her liberal agenda may be further left than some in the Democratic establishment would prefer, she is a team player who is seeking to lead the party — not stage a hostile takeover of it.

Martin provides a lot more detail about the quiet courtship Warren is carrying out aimed at national and state party operatives and elected officials. But the bigger picture it paints which differentiates Warren from Bernie Sanders is that Warren is unambiguously a Democrat, while Bernie’s relationship with the party whose presidential nomination he is again seeking is, well, complicated. He is running for Senate reelection this year as an independent, and only running for president as a Democrat because the DNC is forcing him to make this choice. His arm’s-length attitude toward the party arguably gives him a boost among progressive independents who can participate in Democratic primaries in a majority of states; he famously did better in open-primary states in 2016. But other primary voters, given a choice between an actual Democrat and a tactical Democrat, may prefer Warren.

It’s not simply a matter of Warren’s willingness to work in conjunction with the party organization in a general election, or even the emphasis she places on Democrats winning the Senate to give Trump’s successor a better opportunity to govern. She also embraces a “theory of change” that treats Democratic members of Congress as the principal vehicle for the implementation of her agenda. She very clearly, for example, favors abolition of the Senate filibuster. Sanders, by contrast, isn’t sure he wants to change the Senate’s rules, and instead is touting a “political revolution” that will somehow overcome resistance to his ambitious policy goals in both parties.

If you are a Democratic Party stalwart — at either the elite or the rank-and-file level — it may be as simple as favoring the candidate who wants a peaceful overhaul of the party agenda than the one who insists on a hostile takeover. And this could be Elizabeth Warren’s secret weapon.