At first glance, Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.) are similar. They’re both older, white and progressive; support Medicare-for-all; and cast politics as a struggle between powerful elite and a virtuous public. Neither grew up with much money. And they both charted unlikely paths into national Democratic politics. No wonder progressives hope that means that Warren and Sanders’s supporters will eventually unite into a bloc that helps one of the two win the nomination and the presidency.

But it’s not that simple.

Sanders and Warren have clear differences in style, emphasis and attitude toward our political systems that have helped them cultivate different, rather than interchangeable, bases of support in the 2020 primary. If either progressive wants to win in 2020, they need to do more than try to pick up the other’s voters. And Warren seems to have a better grasp on that reality than Sanders.

Warren’s coalition is a product of both her policies and her personal style. Unsurprisingly, Warren, does well with voters who say they’re very liberal or liberal and gets less support from self-described moderates. But her support isn’t entirely due to her policy positions policy: Rather, her hyper-wonkish approach attracts a solid number of white-collar professionals and drives up her numbers among voters with high incomes and a lot of formal education.

Warren’s progressivism is such that it allows her to walk the line between insider and outsider. She’s been a Democrat for her entire career in electoral politics and seems to focus more on having “a plan for that” than starting a full revolution. But she shows what seems like a genuine dislike for Wall Street, pharmaceutical companies and the other normal targets of left populism. That stylistic mix shows up in the polls: Warren’s coalition is made up of a combination of those who supported Sanders in 2016 and those who preferred Hillary Clinton.

This coalition has its weaknesses. Warren has yet to fully break through with nonwhite voters. And there are a lot of white Democrats without a college degree who might initially prefer Joe Biden or Sanders. But overall, Warren’s footprint seems to be growing — unlike that of Sanders, who, as FiveThirtyEight has documented, is holding on to a weird slice of his 2016 coalition rather than building his base.

Polling suggests that Sanders is mostly winning a subset of voters that he already won in 2016. That includes some ideological liberals who see Warren as an acceptable second choice; some anti-establishment voters who like Sanders because they think the political system is “rigged”; and some voters who liked him last time and aren’t paying much attention to the election yet. But it also includes a mishmash of voters who prefer him for stylistic or demographic reasons.

Sanders has shown significant resilience among downscale voters. He tends to do best among voters with lower incomes and less formal education. Some of these voters probably like his specific policy decisions. But some of them are probably just there for his style, and that style is very different from Warren’s. Sanders’s political rhetoric is pugilistic, direct and aggressive in a very male way. And Sanders may be grabbing some voters who want a male candidate. Alexander Agadjanian, a researcher at MIT, recently found that Sanders’s support increases with voters who score higher on the so-called hostile sexism scale, which measures agreement with statements such as “women seek to gain power by getting control over men” and “women are too easily offended.” The likelihood of voting for Sanders increased with voters who got a higher score.

That’s not to say that all Sanders voters are sexist — most aren’t. Agadjanian told me that only 23 percent of Sanders supporters had an above-neutral level of sexism on this scale. But it’s plausible that sexist voters (or those who are more neutral on gender issues) may consciously or unconsciously gravitate to Biden, Andrew Yang or some other male candidate rather than Warren.

Sanders probably can’t win all of Warren’s voters, and vice versa. Warren may be too establishment-friendly for some of the more fiery “burn it all down” style Sanders voters, and some of the less feminist or more downscale Democrats might not see Warren as a third, fourth or fifth choice.

And Sanders might be too much of an old-style socialist class warrior to bridge the gap with Warren’s affluent suburban and older liberal fans. Progressives might want to treat Sanders and Warren voters as a progressive plurality. But Warren and Sanders fans are too different to naturally fall into a coalition together.

The right solution for both candidates is to cast a wide net and not just look enviously at the vote share of other progressives. For months, Sanders hasn’t had much success with this. His national vote share has been stagnant, and his strategy is basically identical to his (failed) 2016 method. Warren, on the other hand, has been gaining in the polls and trying to fuse together parts of the Sanders and Clinton coalition. And that plan seems a lot more likely to succeed than the Sanders revolution.

Read more: